Manchester United’s hopes of Champions League qualification and winning the FA Cup have been engulfed in a defensive crisis after Lisandro Martínez and Victor Lindelöf were ruled out for a minimum of a month due to muscle problems. Erik ten Hag’s team are in sixth place on 48 points, 11 behind Aston Villa in fourth and nine from Tottenham, who are fifth, having played a match less, ahead of Thursday’s trip to Chelsea. Martínez and Lindelöf’s respective injuries will cause both defenders to miss at least five league games plus the FA Cup semi-final against Coventry on 21 April. The loss of Martínez is a particular blow as he is one of Ten Hag’s frontline defenders and had just returned from a knee problem suffered on 4 February against West Ham when coming on as a substitute in Saturday’s draw at Brentford. Before this the 26-year-old had also been out from mid-September for five months due to a second serious foot injury, the previous one ruling him out for the last month of last season. The absence of Lindelöf means Ten Hag is without another senior defender, the Swede having started at Brentford, with another centre-back, Harry Maguire, coming on as a replacement following the injury issue he suffered during the international break with England. Ten Hag also has Luke Shaw and Tyrell Malacia unavailable because of injury, leaving only Maguire, Diogo Dalot, Aaron Wan-Bissaka and Willy Kambwala as the fit recognised defenders. He may be forced to field Casemiro, also a replacement at Brentford due to his own recovery from injury, in central defence at Chelsea. A United statement said: “Victor Lindelöf and Lisandro Martínez will be out of action for at least a month due to muscle injuries. Lindelöf was withdrawn during the second half of last Saturday’s Premier League game against ­Brentford with a hamstring problem. “Victor was replaced by Martínez after 69 minutes, as the Argentina international made his first appearance since early February. Unfortunately, Licha has now sustained a calf strain in training and is unavailable for the next few games.”