Sergei netted a spectacular opener shortly after being off the field for some eight minutes for treatment.
"That's what Sergei's all about," said Sully. "He's not been playing in too many games this year, he's been coming on as sub and bits and pieces like that.
"But he's a great player and he's always going to score goals for you. On the night I thought he did very well, ran his legs off and ended up scoring a great goal."
Reflecting on a night's work well done, Sully joined with Simon Davies in saying that the all-important factor is a place in the next round.
"The important thing was to get in the hat. Maybe we didn't play as well as we have done in recent weeks, but we scored two great goals and defended well and we're in the hat - so it was a good night's work.
"Their goal was disappointing, it was literally the last kick of the half. But we defended well up until then and it was just a case of keeping going and getting another chance. The ball dropped to Simon and he stuck a great little shot into the bottom corner - and that was it really.
"It's nice to get a home draw, but we've got a couple of league games before then, so we'll worry about that later."
Neil Sullivan paid tribute to Sergei Rebrov after the Ukrainian dynamo set us on our way to Worthington Cup triumph over Fulham.