The England international scored six goals and recorded 10 assists for Aston Villa in the 2020-21 Premier League season, before joining City in August last year for a league-record fee of £100 million.
However, Grealish has struggled to replicate those numbers since moving to Manchester and has failed to score or assist this season.
He was criticised for his performance in City's 2-1 Champions League win over Borussia Dortmund on Wednesday, after he was unable to influence the game and was taken off as part of a triple change in the 58th minute.
"We didn't sign him for the incredible goals and assists he got at Aston Villa. It was another reason," Guardiola told reporters ahead of City's league trip to Wolverhampton Wanderers later on Saturday.
"When he played he did it, but he competes with the top, top players as well. He knows it perfectly but never complains. He's a nice guy. In the game, he's one of the first players to help the team and in training sessions he's always there.
"So I'm delighted about his behaviour and everything. He understands us, we can understand him and he just needs to have a little bit of continuity that I tried to give him and because he deserves it."
City are second in the Premier League, trailing leaders Arsenal by one point, while Wolves are 15th in the standings.
