Sadly for Manchester United Lisandro Martinez will not be available for the first leg because he will serve his one match ban after picking up his fifth yellow card again Real Soceidad. He will be a big miss but united has other center backs like Maguire and Lindelof. I predict Lindelof will start in his place if he is fit or we could see Luke Shaw at the center back after his excellent performance when he was deployed there. Maguire could also be another option but I doubt he can be trusted in this match by Ten Hag. Overall Martinez will be a big Miss in the match
Maguire wasn't participating recently as he was supposed to move to Inter Milan. In addition, he was among the lineup in only 4 matches this season. Therefore, I think it's difficult for him to start the match against Barcelona. For Martinez, missing the first leg is better than missing the second one, which will be more decisive in my opinion.