Chambers turned professional for the 2007 season and competed at the 2007 World Championships in Athletics. He made it to the semi-finals of the individual 400 m, but greater success came in the relay, as he took fourth place in the final for Jamaica. His next major competition was the 2008 Summer Olympics. He again was a semi-finalist in the men's 400 metres, but the Jamaican relay team performed poorly in the event final, failing to match their time from the heats and finishing in last place. He was the Jamaican champion the following year, but his third global appearance – at the 2009 World Championships in Athletics – held similar results; he finished third in his semi-final and was eliminated in the heats in the relay.[5]
In the 2010 season he competed at the World Indoor Championships for the first time. He was a 400 m semifinalist but an injury to Ayre in the relay meant the Jamaican relay team did not finish.[6] He improved his personal best to 44.54 seconds with a run at the Herculis meeting in Monaco, finishing second behind compatriot Jermaine Gonzales.[7] He was selected to represent the Americas team over 400 m at the 2010 IAAF Continental Cup and he won his first medal at a global competition. He ran near his personal best, recording 44.59 seconds, to take the silver medal behind his teammate Jeremy Wariner.[8] He closed the competition by running the anchor leg of the relay for the Americas team which won in a championship record of 2:59.00, breaking the USA's 29-year-old mark.[9]
