Gareth Southgate believes it is unfair to question Luke Shaw’s competitive courage and vigorously defended the Manchester United left-back in light of José Mourinho’s thinly veiled attack on his own player for pulling out of the game against Swansea City.

Southgate pointed out that Shaw was still suffering “physical and psychological aspects” from breaking his leg in two places 14 months ago and England’s caretaker manager also spoke in defence of Chris Smalling at a time when Mourinho is clearly aggrieved that the two defenders opted out of the 3-1 victory on Sunday.

Mourinho’s anger was clear after the game when he confirmed Smalling and Shaw had ruled themselves out and proceeded to talk at length about having to trust his players, noting how many sports people went through the pain barrier and the “difference between the brave, who want to be there at any cost, and the ones for whom a little pain can make a difference”.

Those comments have hurt and surprised Shaw, given the seriousness of his injury and the fact he played in discomfort during United’s Europa League defeat by Fenerbahce last Thursday. Mourinho is also understood to have given Smalling a particularly hard time when he returned to training. Both players have been made unavailable for England’s games against Scotland on Friday and Spain the following Tuesday.

Southgate said he trusted the word of the medical staff at Old Trafford and, while he chose his words carefully so it was clear he was not picking an argument with Mourinho, he made it clear he did not understand the United manager’s comments when the club’s doctors were backing the players’ accounts. His information has been relayed to him by the FA’s medical team, in direct consultation with their United counterparts, and is that both players have legitimate problems. In those circumstances Southgate said it would be wrong to think of them as “flaky” or unwilling to put their bodies on the line.

“There is a medical issue,” Southgate said. “If Shaw wasn’t fit to play – and he was with us in September under Sam [Allardyce] and was feeling problems with the leg back then – there’s clearly something. After an injury as severe as that we have to handle that with care.

“Chris hasn’t played for the last four games. Luke has but we’ve known he has had ongoing difficulties coming back from a very serious injury. If they had played and we weren’t at least having a look at them, it would be different. But if they haven’t played, there’s obviously something wrong. Obviously it’s a difficult one because I don’t know the reason for the comments José’s made.”

Mourinho had talked about needing players who understood that “for the team you have to do anything” and the criticism of the two defenders was implicit in various other statements, including the observation that if he was “to speak with the many great football people [in United’s past], they will say many times they played without being 100%”.

The impression it left, perhaps deliberately, was that Shaw and Smalling had let the team down, opting out of a game where both could have played, but Southgate made it clear he accepted their version of events and did not think of either player as lacking mental strength.

“I don’t know Chris well but that wouldn’t be my impression, having worked with him,” he said. “Luke, I know well and Luke has had a really toughinjury. There have been players, when I was playing, who maybe found England was a bit too much for them. But Luke has played with us right through [the age groups] and Chris has had a lot of games for England, so I don’t think that is the situation for them.

“They have a moment with their club where they are not fit and that’s ruled them out for us this time. We employ a medical team to give us good professional advice, and both medical teams are clear on where that situation is.”

Meanwhile, West Ham’s Aaron Cresswell has received his first England call-up. He and Sunderland goalkeeeper Jordan Pickford will link up with Southgate’s squad this week after the withdrawals of Danny Drinkwater and Fraser Forster.