The midfielder has struggled for form after recovering from shoulder and knee injuries picked up at the end of last season.
But the 29-year-old show-ed a glimpse of his quality on Tuesday night, scoring a wonderful 20-yard volley to seal a 2-0 FA Cup win against Accrington Stanley.
Leven had earlier set up the first goal, delivering a corner which James Constable headed in.
Lewis acknowledged it had not been easy for Leven after missing the vital physical preparation in the summer, but felt Tuesday’s goal was a sign of better things to come.
He said: “He’s a terrific player. He’s one of those players who will always put himself on the pitch when he’s not 100 per cent.
“Obviously he missed pre-season and is working his way back in. It’s not going to happen overnight.
“By his own admission he might have thought he didn’t have a great game, but he’s created a goal and scored a goal.
“Not many people at our level could have produced that bit of quality.
“He’s a confident boy anyway and believes in his ability, but any time you score it gives you a lift.
“He’s not the kind of lad who needs it. He knows his qualities and the more games he plays, the fitter he’ll get and the more influential he’ll be.”
U’s boss Chris Wilder said last month he believes when the Scot is in form he has the ability to be the best midfielder in npower Lea-gue Two.
Everyone at the club will be hoping Tuesday’s performance will be the catalyst for a sustained im-provement in performance over the all-important festive period.
Constable, who claimed his seventh goal of the season from Leven’s set piece, returned the favour by teeing up the second goal, and the striker was delighted.
He said: “When he’s in those sort of positions with a bit of time, he has a great strike on him.
“I knew the second it left his foot it was going to be going goal-bound and it was nice to see it go in.”