Remi Garde will be in the dugout at Villa Park for the first time since being handed the job of reviving the former European champions, having observed from the stands as they were beaten 3-1 by Tottenham Hotspur on Monday.
The Frenchman could not have been given a tougher first assignment with City top of the table and celebrating a fine win at Sevilla in the Champions League.
But Pellegrini believes Villa will pose a greater threat with players eager to impress Garde.
"Always when you have a new manager, you have some reaction," Pellegrini told reporters.
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"They're at the bottom, they have a new manager, so they have the motivation not to be relegated.
"He (Garde) was at (Manchester City's training ground) Carrington two years ago but I don't know him too much.
"He was a friend of Patrick Vieira's so he wanted to talk about football and working -- he's a young, experienced manager at an important club like Lyon. I am sure, after this game, he will have a good career at Villa."
Sunday's game has come too soon for Spanish playmaker David Silva who has almost recovered from an ankle injury, but midfielder Fabian Delph could be in line for a return after a lengthy layoff with a hamstring injury.
He came off the bench against Sevilla and might do so again at Villa Park.
"Maybe (Gael) Clichy and Delph are not ready to start but they are to be on the bench and that's important," Pellegrini said.
"Fabian played at Villa for a long time but he's a professional player and now plays with us.
"I know he wants to play as he's had so many injuries."
(Reporting by Martyn Herman, editing by Ed Osmond)
