has told new goalkeeper to keep slamming his defenders after an incident involving .
Onanaduring United’s friendly defeat to  on Sunday.
The summer signing from Inter Milan berated former captain Maguire for a sloppy pass to Christian Eriksen – which led to a Dortmund chance – and Onana subsequently forced into making a save.
Onana and fellow defender Martinez feels the Cameroonian’s passion will only help the side.
‘It’s better for [it],’ Martinez said. ‘If you are focused, you can fight with your team-mates as well.
‘You need to make sure everyone is really sharp, but nothing happened. It’s part of football.
‘He has a big personality, he can play football, he can deal with the pressure, he’s really positive, he’s a leader. That’s the style of Manchester United.’
Quizzed about Erik ten Hag’s decision to strip Maguire of the United captaincy this summer, Martinez added: ‘It’s the coach’s decision and we need to respect it. He’s the boss.
‘If he takes the decision, as a player we need to keep going. Bruno [Fernandes] is a good leader and a good person as well. He’s really positive in the dressing room and I think he deserves it.’
Maguire, meanwhile, has been linked with a move to fellow Premier League side West Ham this summer.
