For the third time in less than 10 months, United were defeated by opponents reduced to 10 men before half-time as they fell to rivals Manchester City over the weekend.
The Red Devils now have four points from a possible 12, with one win, one draw and two defeats as pressure piles on to manager Michael Carrick who many are asking to be replaced.
United are 13th after four matches and the side are yet to establish a consistently productive front line and have looked toothless since the beginning of the campaign.
Speaking on The Rest Is Football podcast, former England striker Lineker suggested that he was confused by the refusal to start key goalscorer Sesko.
"Up top... they look like they’re lacking. They’ve got (Benjamin) Sesko on the bench. It’s odd, he comes on and he has scored in games but you wonder why he’s not getting a starting place.
"Obviously they’ve got Cunha, he’s more of a ten than a nine, (Bryan) Mbeumo plays mostly off the right, obviously (Marcus) Rashford is on the left."
Lineker then argued that Carrick waited far too long to introduce Sesko: "You kept looking at it and thinking, 'If you get someone up top... are you going to bring the big man on?', and he did come on a bit late."
Alan Shearer than gave his opinion on United’s attack, which he believes to be lacking when compared to the likes of Arsenal or Manchester City.
"There’s talk of how they’ve strengthened their forwards and they’ve strengthened the midfield but they didn’t strengthen defensively," Shearer explained. "I’m not 100 per cent certain that they’re that great up top anyway. I think they’re all right, they’re decent. But when you compare them to a lot of the big teams..."
United entertain Brighton in the Carabao Cup tonight, before a trip to Fulham four days later in the Premier League.
Results must turn around or Carrick may face the sack before he can lift this campaign off the ground.