A graduate of the Aston Villa Academy, he was loaned from Aston Villa out to Port Vale and Wycombe Wanderers in 2008, before spending the 2009–10 campaign on loan at Lincoln City. He made his Premier League debut in November 2010, and went on to become a regular first team player in the 2011–12 season. He was largely absent from the first team for the next two seasons, and was loaned out to Bolton Wanderers in September 2014, and then Wigan Athletic in January 2015. He signed with Chesterfield in September 2015, before signing a deal to join Australian side Perth Glory in April 2016, however, he decided to terminate the contract for family reasons and signed for Gillingham in October 2016.
Born in Melbourne, Australia and raised in Perth, Western Australia, Herd signed for Aston Villa from Australian club Bayswater City SC in February 2005, along with fellow Australian Shane Lowry, initially in a deal that was made up of a two-year Youth Training Scheme followed by him signing a one-year professional contract with the club. He made 19 appearances and scored twice for Aston Villa Reserves during his YTS campaign, as well as 21 appearances and 1 goal for the Academy. Herd was also part of the squad that won the HKFC Philips Lighting International Soccer Sevens in May 2007, and was rewarded with a two-year contract following the success. He played in a variety of positions in his early career, most notably in central-midfield and on the right-wing, although in the 2007–08 Reserve season, he was heavily deployed at right-back. In July 2008, Herd was awarded with a new two-year deal. On 17 December 2008, he was selected on the bench for Villa's UEFA Cup match against Hamburger SV in Germany.
In January 2008, Herd signed on a one-month loan deal (subsequently extended) for Port Vale, and made his debut in the following match against Millwall. Herd received the first red card of his career in early February 2008, as Vale lost to Bristol Rovers. On his return to the team after suspension he scored two early goals in the 3–2 defeat to Hartlepool United on 12 February. After returning from Vale Park, Herd then signed a one-month loan deal with Wycombe Wanderers in March 2008, with Wycombe needing to strengthen their midfield numbers following injuries and a suspension. Herd started three matches and made a substitute appearance in another, to play a total of four games during his spell. He returned to Villa after he was left on the bench for the match against Grimsby Town on 15 April.
Herd featured for Villa's first team during Villa's pre-season for the 2009–10 season, and despite missing a penalty in the shoot-out with Juventus in the Peace Cup final, he still finished on the winning side in 2009. On 27 November 2009, Villa allowed Herd to join League Two side Lincoln City on loan until the new year. Villa granted him permission to play in the FA Cup, clearing the way for him to make his Lincoln City debut against Northwich Victoria two days after joining. Herd scored his first Lincoln goal in a 3–1 defeat to Rochdale on 12 December. Having established himself in the first eleven, Herd extended his loan with the "Imps" until the end of the season.
Through the previous season's loan stint, Herd had become a very popular player among "Imps" fans and he almost rejoined the club in August 2010, although the season-long loan fell through at the last minute. This allowed him to make his Aston Villa Premier League debut against Manchester United on 13 November 2010, when he came on as a late substitute in the 2–2 draw at Villa Park. On 21 November, he made a substitute appearance by coming on in the 81st minute for midfielder Jonathan Hogg in a 2–0 defeat to Blackburn Rovers at Ewood Park. A week later, he came off the bench late into a 4–2 loss to Arsenal at Villa Park. On 10 January 2011, Herd scored a hat-trick as the Aston Villa reserves recorded a 10–1 victory over Arsenal reserves. In January 2011 he signed a contract extension with Villa, tying him to the club until 2014. Herd made his first start for the "Villans" in a 3–0 defeat to Manchester City in the FA Cup Fifth Round. Due to the injuries and suspensions of a few senior defenders at Villa, Herd then followed this making his first Premier League start for Villa, lining up in at right back, in the match against local rivals, Wolverhampton Wanderers at Molineux on 19 March. At the end of the 2010–11 season, Herd made seven appearances in all competitions.
He played as a right-back against Wolverhampton Wanderers in his first Premier League game of the 2011–12; his performance earned him the man of the match award and special praise from boss Alex McLeish. He came back in to the side for the home game against West Bromwich Albion on 22 October, playing in a defensive midfield role. However, he was controversially sent off by referee Phil Dowd for an alleged stamp on Jonas Olsson in the 36th minute. Villa manager Alex McLeish defended the young defender, maintaining that he had "done nothing wrong". However, Jonas Olsson insisted that Herd kicked out and deserved his dismissal. It was confirmed two days later on 24 October that Aston Villa had appealed against the decision. The appeal was successful, and the suspension quashed. In December 2011, Herd had signed a new four-year contract, keeping him at Villa Park until 2015. He scored his first top-flight goal in a 1–1 draw with Liverpool at Anfield on 7 April. On 2 May, he was recorded on video taking part in an early morning "nightclub brawl", along with team-mates James Collins and Fabian Delph. He said that his actions "were out of character", and was forced to pay a club fine as manager Alex McLeish called the incident a "slur on the club".
Herd scored his second goal for Villa in a League Cup win over Tranmere Rovers on 28 August 2012. He ended the 2012–13 campaign with 13 appearances to his name. However, he featured just twice in the 2013–14 season before the club announced that he would be unavailable indefinitely for 'personal reasons' in March 2014.
He returned to Villa at the start of 2014–15 season after spending some months training with his father in Birmingham. On 23 September 2014, he joined Championship side Bolton Wanderers on a one-month loan. The following day he made his debut for the "Trotters" at right back in their 2–1 League Cup defeat to Chelsea at Stamford Bridge. His time with the "Trotters" was blighted by injury and after only three appearances at the Macron Stadium he returned to Villa with Wanderers manager Neil Lennon stating he was unwilling to extend the loan spell while Herd's fitness was in doubt. After pulling out of the Australian squad due to an Achilles injury picked up in a training session, he returned to the Championship by joining struggling Wigan Athletic; manager Malky Mackay stated that "I feel that his energy, his athleticism and his tenacity will be things that can really help us out". However his loan was cut early a month later as he required surgery for a season ending medial ligament injury. He was released in the summer by Villa manager Tim Sherwood.
Herd signed a four-month contract with League One side Chesterfield in September 2015. In January, he signed a contract to keep him with the "Spireites" until the end of the 2015–16 season.
On 28 April 2016, Herd signed with Australian A-League side Perth Glory. However three months later his contract with Perth Glory was terminated by mutual agreement due to him not managing to relocate his family to Perth.
Herd signed a one-year contract with League One side Gillingham in October 2016. He made 14 appearances across the 2016–17 campaign, and was released by manager Adrian Pennock in May 2017.
Herd returned to Australia and signed a two-year contract with Western Sydney Wanderers in July 2017.
Herd was selected in Australia's final under-20 Squad for the 2009 FIFA Under-20 World Cup in Egypt.
As both of his parents are Scottish, Herd was eligible to represent Scotland. In September 2011, his agent Darren Jackson and former agent Phil Williams confirmed that Scotland manager Craig Levein was aware of this and had been following the player's development. His father Willie said he had encouraged his son to play for Scotland, but that he was likely to reject any approaches in favour of continuing to represent Australia.
He received his first call-up to the Australia senior squad in November 2011, when he was selected for the World Cup Qualification matches against Oman and Thailand, but had to withdraw from the squad because of injury. He was called up again in August 2012, but was forced to withdraw from the squad due to a quadriceps strain. Herd made his debut for Australia in a friendly against Belgium on 4 September 2014.
Herd was named as part of Australia's squad for the 2015 AFC Asian Cup. However, Herd injured his Achilles tendon in a training session prior to the match against Oman, ruling him out for the remainder of the tournament. Australia went on to win the tournament for the first time after beating South Korea in the final.As of 13 July 2017
AFC Asian Cup: 2015