August is traditionally the height of selling season at Chelsea, and centre-back will be a focus of outgoing activity from Stamford Bridge this month.Even with Trevoh Chalobah set to join Como for a fixed fee of €30million (£26m, $35m) plus €6m in add-ons, new Chelsea manager Xabi Alonso still has 10 senior players capable of playing centre-back. As a season without European football nears, he confirmed in a press conference last week that he only wants to work with four or five.How did Chelsea get to this point, who will be sold, who will be loaned and who is firmly in Alonso’s plans? The Athletic’s Chelsea correspondents Simon Johnson and Liam Twomey have their say.Tosin AdarabioyoJohnson: Signed as a free agent when his contract expired at Fulham in 2024, Tosin has enjoyed the role of being one of Chelsea’s few leaders.At 28, he was the oldest player to represent Chelsea last season. His biggest contribution goes largely unseen as he is a positive influence inside the dressing room and at the training ground. Jordan Henderson and Danny Welbeck have been signed to help with that, but this does not mean Tosin now needs to make way.His form has divided the fanbase. Being one of those players who are in and out of the side had an impact last season. However, Tosin showed against Leeds United in the FA Cup semi-final win that he can make a difference when called upon.His position at the club as a squad player or back-up centre-back has been cemented even more now with the arrival of Maxence Lacroix. But if Tosin is content to play just a few games here and there without complaint, then it is worth keeping him around. It would certainly make Cole Palmer happy.Verdict: KeepBenoit BadiashileChelsea would want about £30m for Benoit Badiashile (Julian Finney/Getty Images)Twomey: When he arrived from Monaco in January 2023, Badiashile was considered by Chelsea as one of the three best young left-sided centre-backs in Europe (the other two being Levi Colwill and Josko Gvardiol). It’s fair to say the shine has come off the Frenchman in the three and a half years since.Last season, with Colwill sidelined by an anterior cruciate ligament (ACL) injury, was Badiashile’s golden opportunity to fulfil his undoubted potential and properly establish himself at Chelsea. Instead, he found himself behind Chalobah and Jorrel Hato by the end of the campaign. It’s time for him to move on.Verdict: Sell (asking price £30m)Levi ColwillJohnson: There is no debate about this one: Colwill is staying. Chelsea regard him as one of their ‘untouchables’ and are not interested in any offers.