Chelsea lost 2-0 in a behind-closed-doors friendly to Championship side Portsmouth on Saturday afternoon as they prepare for the return of the Premier League.The secret game against Pompey – revealed to be taking place by Daily Mail Sport earlier this week – involved some Blues players who are rehabbing their way back to fitness.Chelsea face Bournemouth next in the Premier League at Stamford Bridge on Saturday October 10, after this three-week international break has ended. The Cherries are winless in the league under new head coach Marco Rose after five match rounds.Also involved against Portsmouth were some younger players from the Chelsea academy alongside first-teamers, while sources added Xabi Alonso used it for tactical work. It was described by insiders as a training exercise, first and foremost, and so they are not alarmed by the scoreline in any way.Senior stars have been away on international duty, such as Morgan Rogers, who scored the seventh in England’s 7-0 win over Croatia in the Nations League on Saturday.Portsmouth, managed by John Mousinho, are 19th in the Championship and preparing to play the South Coast derby against arch rivals Southampton next. Xabi Alonso’s Chelsea lost 2-0 in a behind-closed-doors friendly to Championship side PortsmouthOne major area of focus for Alonso in this break has been how to stop opponents from scoring. His team have the worst defensive record in the Premier League this season after conceding 12 goals in five games.One decision he will need to make versus Bournemouth is whether to persist with his three at the back, or move to a more traditional system involving a back four.Alonso has shown a fondness for secret friendlies, having set up two in the summer against Crawley and Bromley before their pre-season trip to Australia and Asia. They won those, but not against Portsmouth on Saturday.