On 29 May 2008, Eredivisie side Feyenoord announced the signing of Erasmus on a three-year deal from South African affiliate-club SuperSport United and handed him the no. 15 jersey for the 2008–09 season. He made only four appearances for the Rotterdam club during the campaign and in July 2009 it was announced Erasmus would be loaned to satellite club Excelsior in the Eerste Divisie for the following season. Erasmus, together with compatriot Kamohelo Mokotjo and six other Feyenoord players were loaned to Excelsior as a result of a new partnership between the two Rotterdam-based clubs.

Erasmus was called up to the senior squad for the first time in March 2008 for South Africa’s friendly against Zimbabwe. In doing so, he was in line to break the record then-held by former captain Aaron Mokoena and become South Africa’s youngest ever full international. He did not take to the field and had to wait until 4 September 2010 before he made his debut, coming on as a second-half substitute for Katlego Mphela against Niger in a 2012 African Cup of Nations qualifier. Erasmus had to wait a further three years before scoring his first goal for South Africa, finally netting in a 2014 FIFA World Cup qualification match against Botswana on 7 September 2013.

On 10 July 2010, it was announced that Erasmus would be returning to South Africa to rejoin SuperSport United after failing to make the grade at Feyenoord. Eleven days after his return, Erasmus made his second appearance for Supersport United and scored what was described as a “sensational strike” in an MTN 8 loss against Moroka Swallows.

In 2010 Erasmus starred in the award-winning feature Documentary film Soka Afrika which highlighted the plight of young footballers across Africa. He was dating Lauren Koehoorn for 8 years until they broke up in 2018. The couple have two children together.

On 26 May 2012, Erasmus scored the second goal in Matsatsantsa’s 2–0 win over Mamelodi Sundowns in the Nedbank Cup final. He left Supersport United at the end of the following season having made over 50 league appearances during his second spell at the club.

On 23 July 2013, Irvin Khoza, the Chairman of Orlando Pirates, confirmed the signing of Erasmus from Supersport United. The following day Pirates lodged a request to CAF for Erasmus to be registered for the upcoming CAF Champions League campaign. The request was denied, however, as Erasmus had already represented Supersport United in the CAF Confederations Cup earlier in the season. As per CAF regulations, a player is only eligible to feature for one club in CAF inter-club competitions during the course of a season.

On 8 January 2016, Erasmus was named in the 18-man CAF Team of the Year. He had also been nominated for the 2015 CAF African-based African Player of the Year award alongside Orlando Pirates teammate Filipe Ovono but eventually lost out to Mbwana Ally Samatta of Tanzania. Eight days later, he netted a late equalizer in 3–3 PSL draw with Maritzburg United, with Pirates having trailed 3–0 in the first half. The goal proved to be Erasmus’ final contribution for the Sea Robbers as the following week he completed a move to French Ligue 1 side Rennes.

On 28 January 2016, Erasmus signed for Ligue 1 club Stade Rennais on a two-and-a-half-year deal. He made his debut for the club on 13 March, coming on as an 80th-minute substitute for Pedro Henrique in a 2–2 draw with Lyon. His only other appearance for the season came on the final day of the campaign in a 2–1 loss to Bastia which saw Rennes end eighth in Ligue 1. He made his first appearance of the following campaign in Rennes’ opening match of the season, coming on as a second-half substitute for Gélson Fernandes in a 1–0 defeat to Nice.

On 21 January 2017, Erasmus signed for Ligue 2 side RC Lens for the remainder of the season. He scored once in 12 league appearances for the club, with the goal coming on the final day of the season as Lens narrowly missed out on promotion. He returned to Rennes at the end of the campaign but, by February 2018 failed to make another appearance and was released by the club.

On 26 March 2018, Erasmus signed a two year-deal with AFC Eskilstuna, newly relegated to Superettan, Sweden’s second tier. He went on to play 11 league games for the club, scoring twice, during the season.

On 17 August 2018, he transferred to Portuguese club Vitória de Setúbal in the Primeira Liga.

On 18 December 2018, Erasmus signed for PSL side Cape Town City.