"That was definitely one of the luckiest goals of my career - but they all count!" he laughs.
"I saw one of their defenders running back and thought he'd get back to it, but when it hit the back of the net I was overjoyed, so were the lads and so were the fans."
In a hectic end to the game, Vassell came on to replace another substitute, Daniel Sturridge, who was injured in the incident that led to Elano's 79th minute penalty.
He told City's website: "It was crazy towards the end. Daniel got a knock and maybe the ball should have been kicked out of play, but that said I wasn't even there, I was in the toilet at the time! I came back up the tunnel and was straight back ready to come on - then they scored and I had to wait a bit again.
"I wanted to see how Daniel was, because he has an important game coming up for the youth team. I was only on for a short time and wanted to make things happen, and fortunately that's what happened."