Kean's fine display in his side's 2-0 Serie A win against Cagliari on Tuesday was overshadowed by allegations that the 19-year-old, who scored Juve's second goal, was the target of racist taunts.
The Italy international celebrated his late strike in front of Cagliari's supporters, and team-mate Bonucci said after the game that Kean should take 50 per cent of the blame for the incident because he incited the home crowd.
Defender Bonucci later clarified his remarks via social media, saying that he was "too hasty" in expressing his thoughts and "firmly condemned racism".
"I was surprised at this happening in Cagliari. Usually it is a good atmosphere, so I was surprised," he told a media conference.
"Bonucci made a mistake but I am sure he probably wanted to say something different because I am sure Leonardo is not racist.
"He made a mistake. We can only be an example for people but it's difficult to solve the problem [of racism in football]."
Sarri's Chelsea take on West Ham in the Premier League at Stamford Bridge on Monday.
The Blues have found form of late, having won their last three Premier League games.
"Now he is tactically a very good midfielder. At the beginning of the season he was a very offensive midfielder. Now he is complete, I think."
Loftus-Cheek has only started 11 games for Chelsea this season after injury problems earlier in the campaign, and Sarri said physios are still monitoring his condition.
"We need to check every day the condition of his back," Sarri continued.
"This morning he had only a recovery session because he needs time to recover after a match. The problem in this moment is that probably he is not able to play for 90 minutes.
"It's a problem of course, but I think our doctor is able to take control of the situation."