Manchester United's 24-day break between matches was supposed to be a period of rest and tactical refinement. Instead, it seemed to leave them rusty and off the pace, as a sharper Leeds United side dominated the opening period at Old Trafford. The halftime whistle was met with a chorus of boos from the home support, a clear message to manager Michael Carrick about the unacceptable performance.

While United showed some improvement after the break, the game's most damaging moment came with Lisandro Martínez's needless red card. The fiery Argentine defender's dismissal leaves a massive hole in the heart of United's defense at the worst possible time. He will now miss three critical Premier League fixtures: a tough trip to Chelsea and home clashes against Brentford and rivals Liverpool.

Each of those matches is vital for United's top-four aspirations, and the defensive crisis is deepening. With Harry Maguire also facing a potential suspension from the FA, Carrick could be forced to field an incredibly inexperienced center-back pairing of teenagers Ayden Heaven and Willyam Yoro at Stamford Bridge. After a relatively smooth start to his tenure, Carrick is now facing his first major tactical and selection headache, with the club's Champions League hopes hanging in the balance.