Lisandro Martínez’s view that Jason Wilcox is failing as Manchester United’s director of football reflects wider dressing-room frustration over recruitment and squad depth, although the outburst caused at least one teammate to challenge the defender to identify who he believes is not good enough for the side.

Martínez may face internal ­disciplinary action over extensive criticism of the hierarchy made in two broadcast interviews after Tuesday’s 2-0 Champions League defeat at Atlético Madrid. The players had Wednesdayyesterday off so any action would not be taken before their return to training on Thursdaytoday.

Martínez directed his anger at Wilcox and what he referred to as “the top” of the club, saying not enough players had been signed and questioning the scale of investment, and that “more ambition” was needed. He said: “We don’t have the best squad at the moment compared with other top teams.”

Martínez’s comments prompted a challenge from at least one teammate before the flight back to ­Manchester and caused a heightening of tension. The Argentinian did not appear to explicitly call out his teammates, saying merely that “as players we have to do more”, and claimed that last season the squad had “created the base to build an amazing team”.

Although the sway of dressing-room opinion is with Martínez, his remarks are also seen as the centre-back considering his future, because he is out of contract next summer.

Defeat at Atlético left United with two wins this season, having taken six points from their first six Premier League matches, the club’s poorest league start for 40 years. The run of form has put the head coach Michael Carrick under pressure, but Martínez took aim at Wilcox and the rest of the hierarchy. “Tonight it is easy to say the coach, easy to say the players, but also we have to see other areas,” he said, pointing upwards.

“I expect more [investment], 100%. I expect more from our technical director [Jason Wilcox]. I have to be honest, as players we have to do more, but it is also important when you make a strong squad to be ready for this kind of night.”

Wilcox, the executive in charge of transfers, oversaw £155m of spending in the last window on Youri Tielemans, Andrey Santos and Carlos Baleba. The decision to recruit three midfielders while not strengthening other areas has been met with puzzlement among the squad, particularly as Wilcox was looking for a left-back, with Newcastle’s Lewis Hall the prime target.Luke Shaw is United’s only senior player in that position and his 12-year career at the club has been plagued by injury. The 31-year-old missed the defeat by Atlético and owing to a muscular problem. The lack of depth at left-back reflects the prevailing view among players that Carrick has been left without the resources to challenge. United were eliminated from the Carabao Cup by Brighton after making eight changes.

Although Carrick led United to third last season, this came after he took over as caretaker in mid-January with only 17 league games to play with the team out of all the other competitions.

Martínez is understood to favour a move to an elite European club outside the Premier League.

On Wednesday night, Martínez released a statement on social media in an attempt to clarify his comments, writing: “I know that, first and foremost, it’s us, the players, who have to deliver, and I put myself at the front of that responsibility.”

He added: “I believe in my teammates, our manager and everyone working to help this club move forward.” Yet he still maintained his post-match comments “reflect how I feel and how much I want to see this club competing for the biggest honours”.