The former Blues winger broke a 55-game individual Premier League scoring drought to give the R's their first away win since November 2011 and their first triumph at Stamford Bridge since 1983.
"It was a relief. Travelling away from home, we haven't been the best and have been dropping a lot of points. We had to consolidate and try to frustrate them, and I thought before I came on the team did well and after I came on we did better and tried to catch them on the break," he told Sky Sports.
"We just believed that we were going to make a few more chances and one of them we had to take. That's what we tried to do."