Mckay began his career with Leicester City, but was unable to break into the first team, spending some time on loan with Hinckley United. Released by Leicester in 2009, Mckay played for Northampton Town before joining Inverness Caledonian Thistle in Scotland in 2011. After scoring 62 goals for Inverness in three-and-a-half seasons, Mckay was signed by Wigan Athletic in January 2015. He did not hold a regular place with Wigan, and was loaned to Dundee United, Oldham Athletic and Inverness over the next two seasons. Mckay signed for Ross County in July 2017.
Although born in England, Mckay qualifies to play for Northern Ireland through ancestry. After representing the country at various youth levels, he made his full international debut in 2013.
Mckay started his career at Leicester City after being spotted as a youth by scout Bev Ironmonger. At a young age, he was brought into the academy, started to push for the first team and signed a new contract in 2008. Despite impressing with a prolific goalscoring record at academy and reserve team level for Leicester, Mckay was released at the end of the 2008–09 season.
He was loaned, for a month, to Hinckley United of the Conference North, in 2008.
Northampton Town gave Mckay a trial during 2009 pre-season, where he impressed by scoring two goals, including an overhead kick, against Coventry City. After this match he was awarded a one-year contract from manager, Stuart Gray.
Mckay also claimed the honour of becoming the first Northampton Town player to score in the 'new' rivalry with Milton Keynes Dons. He netted in a 3–1 defeat at stadium:mk. His first senior goal came during a 3–0 win over Accrington Stanley. After a couple of months coming on as a substitute without scoring – often played out of position – Mckay scored the winner against Dagenham & Redbridge, in the 88th-minute, during a 1–0 win on Boxing Day. Four weeks later, on 26 January 2010, he scored and provided an assist for Ryan Gilligan, in a 2–1 win over Darlington. This was followed up by in February 2010 when he grabbed a 'brace' in a 4–0 win over Accrington Stanley.
In late April, Mckay signed a new deal that kept him at Northampton, after the club invoked a clause in his contract to keep him. Afterwards, Mckay was happy to confirm his delight at remaining at Northampton Town. At the conclusion of the season, Mckay had made a total of forty-three appearances, including cups, and scored eight goals.
At the beginning of the following season, 2010/11, Mckay revealed his desire to double his scoring tally from the previous campaign. He was given the number 16 shirt, with his previous number 17 jersey being taken by Michael Jacobs. After four games without scoring, Mckay netted his first league goal of the season in a 1–1 draw against Aldershot Town. He also found the target in a 2–0 win over Brighton & Hove Albion in the first round of the League Cup.
On 22 September 2010, Mckay scored Northampton Town's first goal in a memorable League Cup victory over Liverpool at Anfield. Just three days later, he scored again and provided an assist for Ben Tozer in a 2–0 win over Bradford City.
Mirroring the previous season, he then suffered a goalscoring 'drought'. However, this was broken when he scored in consecutive games against Lincoln City and Cheltenham Town.
At the season's end, Mckay had made a total of forty-one appearances, including cup competitions, with a return of eight goals. At the culmination of the season, he was offered a new contract, despite eight players leaving the club on free transfers. Two months later, Mckay left Northampton Town, with rumours circulating that he had agreed to join a new club.
After leaving Northampton Town by mutual consent, Mckay signed for Scottish Premier League club Inverness Caledonian Thistle, along with Aaron Doran from Blackburn Rovers. Upon joining, his Inverness career got off to an unfortunate start after suffering an early injury.
He made his debut for the club on 27 August 2011, replacing Doran during the game, in a 2–1 win over Kilmarnock. However, Mckay's initial time at Inverness was mostly spent coming on as a sub – without scoring – and he was often played out of 'position'. Eventually, on 10 December 2011, he scored his first goal for the club, a header against Dundee United in a 3–2 home defeat. After netting his first goal, Mckay stated that he expected to score plenty more goals for the club. Unfortunately, he continued to find himself being used as a substitute. Nevertheless, his patience was rewarded when in April 2012, he scored twice in a 4–3 loss against Kilmarnock. At the end of the season, Mckay signed a two-year contract, just as his current deal was set to expire. In his first season, he made 24 appearances, scoring three times.
The following season, 2012–13, proved to be a breakthrough for Mckay as he went on a goalscoring run and became a key player for the club. In the opening game of the season, he scored in a 2–2 draw against St Mirren and shortly after, in the second round of the Scottish League Cup, he scored with a header during a 1–1 draw against Stenhousemuir – a game in which Inverness won on a penalty shoot-out. A few weeks later, on 19 October 2012, Mckay scored twice in a 4–1 win over Dundee, and from 19 October to 10 November, he hit four goals in three games. Soon after, he scored the winning goal in a 1–0 victory over Celtic. After the match, Manager Terry Butcher claimed that the success was 'magnificent'. In the Highland derby, fourth-round of the Scottish Cup, Inverness CT and Ross County required a replay to separate them, but Mckay grabbed the eventual winner in the replay. At the end of November, he was awarded the SPL – Player of the Month, along with Butcher and Doran, who won the 'Manager of the Month' and 'Young Player of the Month' respectively. A week later, Mckay scored his first career hat-trick, in a 4–4 draw against Dundee United. Between 24 November 2012 and 26 December 2012, he notched ten more goals (including the Scottish Cup) over seven consecutive games. This outstanding level of performance and goalscoring led to him speculatively being linked with English clubs. The transfer rumours led to Butcher offering him a new contract. The manager also stated that Mckay was happy to remain at the club. Furthermore, Butcher claimed his striker was worth more than Celtic's Gary Hooper. On 19 January 2013, Mckay grabbed his first goal of the calendar year and then scored again in a 3–0 win over Aberdeen. In March 2013, he ended any transfer speculation by signing a new two-year deal. Terry Butcher expressed his delight to the media at securing Mckay's future at Inverness. He 'celebrated' his contract extension soon after, in the Highland derby, by slotting home the winning goal from a penalty in a 2–1 win. He led the top-scorer charts for much of the season and had put himself in the running to win the 'Player of the Year' award. Had he done so, Mckay would have become the first man to win it (from a team other than Rangers or Celtic) since 1990, when Jim Bett claimed the award. Ultimately, however, Mckay wasn't included in the shortlist; instead, team-mate Andrew Shinnie was one of the four nominees.
By the start of the 2013–14 season, Mckay was linked with a move to Bulgarian club Ludogorets Razgrad following their £375k bid rejected by Inverness CT. Mckay started the 2013–14 season with a goal in each of Inverness CT's first three league games, and eventually five in the opening five fixtures, including a double in a 2–0 win over Hearts. His impressive form continued with the only goal of the game away to Scottish Championship side Dundee in the League Cup, and a double in the 3–0 home victory against Hibernian. At that point, Mckay had a goal-a-game return with nine goals from nine matches. Mckay's prolific start to the season was recognised with the award of SPFL – Player of the Month for September. Mckay then scored two consecutive brace in two games between on 12 December 2013 and 21 December 2013 against Hearts and Aberdeen. In the Scottish League Cup final against Aberdeen, Mckay played the whole 90 minutes plus extra time before the game eventually reached a penalty shoot-out, and then went to 'sudden death.' Aberdeen won the match and the Cup after Mckay and Greg Tansey missed their penalties in the shoot-out. Mckay had successfully converted in the penalty-shootout in the semi-final against Hearts. Six days after the Scottish League Cup Final, Mckay bounced back when he scored the only goal in a 1–0 win against Partick Thistle. Two weeks later on 4 April 2014, he provided assist for Doran before scoring the winning goal, in a 2–1 win over rivals, Ross County. In a 1–1 draw against Dundee United on 3 May 2014, Mckay was captain for the match in absence of Richie Foran. He finished the campaign with 22 goals from 46 appearances.
Ahead of the 2014–15 season, Mckay continued to be linked with a move away from Inverness, with clubs in Europe were keen to sign him, as Manager John Hughes said clubs keen to sign Mckay would need be a "exceptional offers". In the 2014–15 season, Mckay started the season when he scored his first goal of the season, in a 2–0 win over Hamilton Academical. However, Mckay struggle to score goals and it took until 8 November 2014 for Mckay to score twice, in a 4–2 win over Hamilton Academical. Mckay went on to score four goals in three appearance between 8 November 2014 and 6 December 2014 against Motherwell and Dundee. Between 1 January 2015 and 24 January 2015, Mckay scored five goals and five appearance, including a double against Kilmarnock.
With his contract due to expire at the end of the 2014–15 season, Inverness agreed to sell Mckay to Wigan Athletic in January 2015 for a deal in the region of £150,000.
It was later confirmed that Mckay signed for Wigan Athletic on 30 January 2015. Following his move, Mckay was given the number 10 shirt. Mckay made his Wigan Athletic debut the next day, when he came on as a substitute for Martyn Waghorn in the 78th-minute, in a 0–0 draw against Ipswich Town. However, Mckay struggled to score and only made nine appearances for the club, eight of them as a substitute. Not only that, Wigan Athletic were relegated to League One at the end of the season.
Ahead of the 2015–16 season Mckay was once again in the transfer spotlight when he was linked with a move back to the Scottish Premiership, with Dundee United making a bid for him. The Dundee United manager Jackie McNamara then said that Wigan had rejected two bids his club had made for Mckay. These bids were rejected despite it appearing likely that Mckay's first team opportunities would be limited following the arrivals of Will Grigg and Craig Davies. Mckay then scored his first Wigan Athletic goal in a pre-season friendly match against Altrincham on 14 July 2015. Mckay then had his shirt number changed from 10 to 19, with his number 10 shirt being given to Davies.
On 27 August 2015, Dundee United agreed a fee of around £200,000 with Wigan to sign Mckay. He signed for Dundee United the following day, but on a season-long loan deal rather than a permanent contract having reportedly failed to negotiate a severance agreement with Wigan. One day after signing for the club, Mckay made his debut in a 2–1 defeat away to Ross County.
On 13 July 2016, Mckay signed for League One club Oldham Athletic on a season-long loan. He made his first appearance for Latics in a pre-season friendly against Huddersfield Town. He scored his first goal for Oldham in an EFL Trophy tie against Carlisle United on 30 August 2016.
Mckay returned to Inverness on loan on 31 January 2017.And scored a spectacular bicycle kick to give Caley the win over Rangers on 24 February 2017, ending their winless streak that stood 15 matches, which started in October 2016.
Mckay signed a two-year contract with Ross County in July 2017, moving from Wigan Athletic on a free transfer, despite having a year to run on his Wigan contract.
Mckay was called up to the Northern Ireland national under-21 football team for the 2011 European Championship qualifiers against the Czech Republic and Iceland. He didn't play in the first match against the Czech Republic but started against Iceland in a 6–2 defeat. His first win playing for Northern Ireland came in a 3–0 success against San Marino.
Mckay was selected for the senior Northern Ireland squad in November 2012, and made his full international début in February 2013 in a friendly against Malta.Personal
SPL Player of the Month: November 2012, September 2013
As of 19 August 2017