Upon leaving school, Baker was contracted by the Manawatu Rugby Union. In his second year out of school he was a part of Manawatu's 2008 national provincial championship squad. He was spotted by coach Dave Rennie and had signed with Manawatu at just 20-years-old. Baker made his debut for Manawatu in the 2008 Air New Zealand Cup competition, coming on as a replacement against Auckland in a Ranfurly Shield match. He went on and made his starting debut against Wellington whilst also scoring his first professional rugby union try.
Returning to Manawatu for the 2009 Air New Zealand Cup, Baker scored three tries, the province's second top try scorer of the year along with three fellow players. He also was suspended from all rugby for eight weeks after allegedly verbally abusing assistant referee Zarne Johnson in an competition match between Hawke's Bay and Manawatu. Baker was also charged with allegedly threatening Johnson.
Baker was signed by the Highlanders after an impressive ITM Cup and New Zealand sevens campaign in 2010, he signed a two-year deal with the Otago based Super Rugby franchise. A stress fracture in his back had ruled Baker out of all rugby for three months which he suffered in Delhi winning gold at the Commonwealth Games. Though he was expected to overcome the injury before the super rugby season started, a scan in February showed the fracture had not mended and he was subsequently released by the Highlanders to their wider training group and was then replaced in the Highlanders squad by Kade Poki.
Andre Taylor was Taranaki's preferred fullback throughout 2011, but Baker, who had re-signed with Taranaki through until the end of 2012, was recalled by the Highlanders despite lasting just one full game during the shortened ITM Cup season. He eventually made his debut for the Highlanders in the opening round of the 2012 Super Rugby season, coming on as a replacement against the Chiefs in Hamilton. Baker made a further six appearances and scored two tries, one such try against the Blues in round nine saw him chase a kick at pace to what ended up being the winning try.
Baker did not return to the Highlanders for the 2013 Super Rugby season, but instead signed with the Crusaders as a member of their wider training group. In November 2013, Baker returned to the Highlanders after a successful ITM Cup campaign as a member of the Taranaki side that won the 2014 ITM Cup Premiership over Tasman. He signed with the side for two years after putting aside his sevens career to concentrate on Super Rugby.
December 2009, Baker shifted north to Taranaki along with Manawatu teammate Andre Taylor, who both signed with the union on a two-year deal. He made his debut for the province starting at fullback against Northland in round one of the 2010 ITM Cup. After being sidelined throughout the super rugby season with a stress fracture in his back, the injury, though, eventually improved and he managed to play several games for Taranaki in their 2011 ITM Cup campaign. Baker was also featured in the squads infamous Ranfurly Shield win over Southland. Heading into the 2012 ITM Cup he had scored nine tries in nineteen games for the province.
He made an immediate impact with his decisive running and ability to spot a gap for Taranaki in 2012. His ability to put a player into space also caught the eye. He finished the year as the first-choice fullback. 2013, Baker was nominated for the sportsman of the year award after a stand-out season. However, Baker was praised for his efforts during the year after been given the back of the year respectively. Baker's humour also won him the personality of the year award and his brilliant try against Bay of Plenty saw him get the try of the year prize for the province.
After a six-week ban for a dangerous tackle playing for the Highlanders near the start of the 2014 Super Rugby season, Baker badly tore a hamstring in club rugby in Dunedin before he battled back to fitness to finally get a start for Taranaki against Northland in the 2014 ITM Cup. He finished the season after being a part of Taranaki's narrow victory over Tasman at Yarrow Stadium to win their first ITM Cup title, being new ITM Cup champions. Baker scored five tries and made a further eleven appearances in 2015.
On 5 May 2016, Baker secured his switch with Italian club Zebre who compete in the Pro 12 from the 2016-17 season. Baker played 519 minutes in 9 games, starting 7 and scored 1 try for Zebre Rugby in the 2016–17 season. He came on as substitute against Worcester Warriors where he scored the 2nd try for Zebre in the 78th minute with teammate Kayle van Zyl scoring the 1st try for Zebre in the game. Baker left the Zebre after the 2017 season.
Baker was selected in the New Zealand Sevens squad for the opening two rounds of the 2008–009 IRB World Sevens Series in Dubai and George, making his international rugby debut at the Dubai Exiles Rugby Ground. In 2009 Baker was named in the New Zealand Sevens trial squad, but went on to play in the England, Scotland, Dubai and George Sevens later that year.
In 2010 he secured a permanent position in the New Zealand Sevens squad, playing in all six tournaments. In the Hong Kong Sevens, he led the New Zealand team in scoring four tries in their semi-final win over Fiji and two tries in their Cup finals loss to Samoa. He was also the top individual try scorer and point scorer of the tournament. Later in 2010 Baker was then named in Gordon Tietjens squad to take part at the Commonwealth Games. He was a stand out in the finals against Australia coming on as a replacement and scoring one of the winning tries to ensure them the gold medal. At the final of the 2012 South African rugby sevens title at Port Elizabeth, Baker scored a hat-trick of tries in New Zealand's 47–12 win over France.
Although the then 24-year-old Baker had only played seven matches for the Highlanders, Jamie Joseph, the Māori All Blacks coach, selected him for the 2012 UK end of year tour to England, playing against domestic club team Leicester Tigers, a specially made RFU Championship XV, and ending against the Canadian national team.