Vassell should then be able to recover in time for the start of pre-season training in July.
"He's had a very, very good season for us," Pearce told the official City website. "He's played in the majority of matches but I do know he has got a hernia problem that needs to be addressed.
"He's not been in the England squad this season and the priority for Manchester City is for him to get medically sorted for next season.
"As the plan stands, as soon as the season finishes he'll be taken be taken to hospital and treated for this hernia.”