The Belgium centre back had been ruled out at the start of the month for around three weeks with the injury which he suffered in January's 1-0 win at Stoke City in the fourth round of the FA Cup.
"He trained with the team yesterday...but we will decide after the last training session," Mancini told a news conference. "We are optimistic."
City are also boosted by the return of the Toure brothers, Kolo and Yaya, from African Nations Cup duty with Ivory Coast for the trip to the south coast to a club hovering close to the relegation zone in 16th place.
"Yaya is an important player for us...we missed him a lot in these 20 days," Mancini said.
His return comes at a key time as the champions, who have 53 points from 25 games, seek to make up ground on leaders Manchester United whom they trail by nine points.
While Mancini acknowledged it was a big gap he pointed out his team had managed to close a more challenging one last season.
"In three months everything can change like last year," he said. "If last year we recovered eight points in six games, then to recover nine points in 13 games will be easy."
With Manchester United facing a huge Champions League last-16 tie against Real Madrid, with the first leg on Wednesday, City will be hoping European matters might distract their rivals and make them drop points.
It is not often the blue side of Manchester would contemplate cheering on the red but Mancini could see the possible benefits to City of continental success for United.
"We are supporting Manchester United to go to win in the Champions League," he grinned.
"When you should play in Champions League against Real Madrid it's normal that you can lose your strength in this game, we hope they lose strength in this game."
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- Stoke City
- Manchester United
- Ivory Coast