Though it is not his usual tradition to admit errors let alone publicly apologised for same, Jose Mourinho has decided to eat the humble pie for once and tender a public apology to one of his players.Mourinho apologised to Henrikh Mkhitaryan for taking him off at half-time of Manchester United's FA Cup win over Derby County on Friday.The Armenia international, who was an unused substitute in the 2-0 Premier League victory at Everton on Monday, was replaced by Romelu Lukaku at the break with the game goalless.United went on to win the third-round clash 2-0 thanks to late goals from in-form Jesse Lingard and Lukaku.Mkhitaryan has struggled badly for form in recent months and has found his playing time limited, but Mourinho insists he only took off the former Borussia Dortmund man for tactical reasons. "[It was] unfair [to take Mkhitaryan off] and I told him that at half-time," the United manager said. "I didn't like what I did. He didn't deserve it, he was playing well, he wasn't playing bad."He had a couple of missed passes but he was playing well and giving a good dynamic to the team."My feeling was just that [Marcus] Rashford is not going to score a goal and because of that I'm not going to lose time and I'm going to play Romelu so then I had to sacrifice a player. Micki was the one that I sacrificed but it's something that I don't normally do but I did at half-time and apologised to him in front of other people because he didn't deserve it."Whether Mourinho's apology will translate to another chance for Mkhitaryan to prove himself is yet to be seen.