Martial came on as a second-half substitute against West Ham on Sunday evening but struggled to make an impact as United slipped to a 1-0 defeat.
The 27-year-old did have a chance to score only his fifth league goal of the season but was denied by Hammers goalkeeper Lukasz Fabianski in injury-time.
Martial was expected to be sold last summer after spending the second-half of last season on loan to Sevilla but Ten Hag decided to keep the Frenchman at Old Trafford.
Ten Hag may face another dilemma over Martial this summer and Premier League legend Shearer believes Manchester United should look to sell.
‘Anthony Martial has had enough time at Manchester United,’ Shearer said on Premier League Productions after West Ham’s crucial win.
‘You don’t need to make any big decision on him because I think the decision has already been made or it should already have been made.
‘He’s been there long enough, he’s had enough chances. He’s not good enough to take Man United to where they want to be.
‘If he was good enough he would be starting on a regular basis and he would be scoring goals. He’s had his time and it hasn’t worked for him, that’s my opinion.’
Former Arsenal striker Ian Wright added: ‘With all due respect to Martial, if you’ve got Wout Weghorst starting in front of you, you’ve got a problem.’
Manchester United have enjoyed a promising first season under Ten Hag, lifting the EFL Cup earlier in the year and climbing into the top-four spots.
But the Red Devils are staggering towards the end of the campaign, suffering a shock defeat to Sevilla in the Europa League and suffering back-to-back defeats in the Premier League.
Manchester United are fourth with four games remaining – one point above Liverpool – and welcome Wolves to Old Trafford next weekend.
‘First half I think it was a decent performance and second half it was below our standards,’ Ten Hag said after United’s defeat to West Ham.
‘We should have been up in the first half, we played good football but one mistake and you are following the effects. We have everything in our hands but we have to bounce back and reset, we have to use this week.’
On United failing to score for the second time in the space of four days, Ten Hag added: ‘Of course it’s disappointing, we created and we had the game in our hands. In front of the goal we need to be more clinical.’
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