Di Matteo's side are engaged in a desperate struggle to catch fourth placed Tottenham as they try to guarantee a place in next season's Champions League, but the Italian doesn't want to risk Terry against the Latics with so many crucial cup matches looming.
Terry suffered the injury during the first leg of Chelsea's Champions League quarter-final against Benfica and was forced to come off after an hour of Wednesday's return clash with the Portuguese side as he was struggling to breathe.
Di Matteo, whose side are five points behind Tottenham, acknowledged that taking another blow to the area would risk a significant period on the sidelines for the Chelsea captain, which is unthinkable given their forthcoming Champions League semi-final against Barcelona and FA Cup semi-final meeting with Spurs.
"With a rib injury, it needs time to heal. Every time you get a knock, you probably go a step back," Di Matteo said on Friday.
"We're just trying to manage the injury at the moment. We'll just have to see how quickly he can recover.
"It's one of those injuries that are difficult to deal with because there's not much you can do.
"It's in a position where it's difficult to make it better.
"We need to just deal with the pain level and give him a bit of time to recover. As with all the players, we always assess the risk factor.
"Sometimes, you can play with a little pain, but if the pain is too much then it is not worth it, because you won't be able to perform at the best level."
Meanwhile, Di Matteo has accused the English Football Association of ignoring Chelsea's concerns about the scheduling of their FA Cup semi-final.
The Blues had wanted next weekend's match at Wembley played earlier than at 1700GMT on Sunday, but have now conceded the FA won't change their minds, leaving Di Matteo furious that the Spurs clash will go ahead just three days before the semi-final first leg against Barcelona.
"I'm very disappointed that common sense hasn't prevailed in this," he said.
"Obviously, they didn't take into consideration anything that we said.
"Barca will have one more day to recover than us and it might give them a little advantage.
"Other federations are very helpful. The English federation hasn't seemed very helpful in our case."
Source: AFP
Source: AFP