Substitute Fabio Borini's long-range strike sealed the Black Cats' first Premier League victory of the season on Sunday but Gus Poyet's men are still four points from safety.
|EVS||Sunderland are Evens with Coral to avoid relegation|
"We've still got a long season ahead of us," the Scot told The Sunderland Echo. "But now we just want to take the momentum from the derby into the next game at Hull.
"We've been able to use the boost from Sunday in training this week but we know it's not one game, we've got a lot of matches coming up and we need to take this into the next ones."
Fletcher's return from a dislocated shoulder has provided a timely boost for new boss Poyet, and the striker feels the squad are united as they look to move up the table.
He continued: "Even when we were tiring, we knew we had a togetherness in the team and we were pushing each other.
"I was getting tired, but Jozy [Altidore] said to me 'come on', and I was doing the same with him.
"That's what we needed to do and then Fab [Borini] came on and scored an absolute screamer."
Altidore, meanwhile, underlined the importance of Fletcher's return, and is confident his presence will serve to boost the entire squad.
He added: "It has been difficult for him because he has been out injured a lot and he was only training a little bit until recently.
"It has been great to have him out training again and when he is on the field in match situations it gives everybody else room to operate and be more dangerous.
"We have worked on set-pieces quite a bit so it was nice to see one work out with Fletch scoring. We just need to get him healthy and keep him that way."