The Red Devils, and particularly head coach Michael Carrick, were already under pressure as they travelled to the Spanish capital following a dismal start to the season left the club 13th in the Premier League and knocked out of the Carabao Cup at the first time of asking.
And Martinez came out swinging as he faced post-match media duties, telling Amazon Prime he felt let down by the club’s executives.
"Really poor. Really poor,” he began, summarising the performance. “I have to control myself a lot but sometimes is a reflection of the mirror of how our club is at the moment.”
He continued, saying United’s squad deserved more substantial summer investment after qualifying for the Champions League last season.
Seething: Lisandro Martinez
AFP/Getty
"We did a fantastic season last season and now we expect more from the top, more players to compete because many teams bring many players as well. Atletico have an amazing team and they deserve to win today.
"I expect more [investment]. 100 per cent. 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."
Martinez then turned attention to his team-mates, saying some of them did not put in the requisite effort to get a result at Atletico.
Pressed as to where United still need to strengthen, he added: “In general. Last season we did everything, we created the base to create an amazing team.
"It is annoying, disappointing coming here and I am not seeing my team trying to get an amazing result here."
Many have called for Carrick’s head to roll as underwhelming performances and subpar results continue to flow, with both Antonio Conte and Eddie Howe currently available on the market.
Martinez leapt to Carrick’s defence, though, saying United would not necessarily benefit from scapegoating another head coach but acknowledging results need to improve.
“I don't think so. He does his best. Every season is different. You can't stay with what you did last season. The teams knows how you play, they know every detail, if you don't change next season is a big problem."
"You can't keep changing, changing, changing the manager. What about other areas? I can't say more.
"Tonight it is easy to say the coach, easy to say the players but also we have to see other areas."