According to a report by Metro on Monday November 2, 2026, former Arsenal and England defender Martin Keown has explained why Manchester United manager Michael Carrick must take responsibility for the mistakes being made by Lisandro Martinez.

The Argentina international has come under criticism following Manchester United's disappointing 2-0 defeat to Chelsea at Stamford Bridge, where he was sent off in the second half.

Martinez received his second yellow card in the 63rd minute after catching Chelsea defender Wesley Fofana with a raised arm. Cole Palmer subsequently converted the resulting penalty to put the game beyond United, following Morgan Rogers' opening goal five minutes after the break.

However, Keown believes the problems surrounding Martinez are not simply down to the defender's individual mistakes. The former Arsenal centre-back has instead questioned the defensive organisation under Carrick and his coaching staff.

Speaking on talkSPORT, Keown criticised the number of errors Martinez has been making and suggested that the coaching team must find a solution on the training ground.

“Everything that could go wrong is going wrong at Manchester United, isn’t it? Key players like Martinez, he makes a mistake in virtually every game. There’s no doubt about that,” Keown said.

The former England international also examined Chelsea's opening goal, arguing that Martinez and Harry Maguire failed to close down Rogers before the forward advanced towards goal.

Keown compared United's defensive reaction with the approach he experienced during his playing days at Arsenal, insisting that defenders must put pressure on the player carrying the ball.

“The Arsenal back-four that we had, we would have rushed up to the ball with Morgan Rogers. The player on the ball is the most important person,” he added.

Keown believes Martinez should have moved forward to put pressure on Rogers, while Maguire also needed to step out rather than allow the Chelsea attacker space to exploit.

“You don’t run away. There’s a chance, if he starts to travel with it, right, he’s going to cause disruption. Martinez has got to come up and over and suppress it. Maguire needs to come up, too,” he said.

He subsequently questioned the work being done by Carrick and his backroom staff during training, suggesting that defensive mistakes of this nature should be identified and corrected before matches.

“So, look, when you are on the training pitch, you know, what are we working on?” Keown questioned.

The criticism comes at a difficult time for Manchester United, who have struggled for results under Carrick. Their defeat against Chelsea left them 17th in the Premier League table with seven points from nine matches, while their winless run in all competitions extended to nine games.

Martinez's own future at Old Trafford has also become a subject of discussion. The defender joined United from Ajax in 2022 for a reported £57 million and has a contract until the summer of 2027, with the club holding an option to extend it by another year.

According to transfer expert Fabrizio Romano, direct discussions between Martinez's representatives and Manchester United are expected in the coming days. His performances, behaviour and the possibility of activating the contract extension are reportedly among the issues to be discussed.

The 28-year-old will also miss Manchester United's upcoming Premier League meeting with Aston Villa because of his suspension.

Meanwhile, Carrick's immediate attention will turn to Tuesday's Champions League league-phase encounter against Roma at Old Trafford, as United look to respond to their disappointing performance at Stamford Bridge.