Gary Neville believes Manchester United still need to work on starting games more quickly following their 3-1 win against Tottenham on Sunday.
After a sluggish opening half-an-hour or so United fell behind to a Son Heung-Min goal, although they were aggrieved to have an Edinson Cavani strike ruled out by VAR minutes before.
They were much improved in the second half, however, and Fred, Cavani and Mason Greenwood goals eventually gave them victory.
Neville was impressed by what he saw after half-time, but has warned that in a post-Covid world with supporters in stadiums United could have been made to pay for their poor first period.
Speaking in his column for Sky Sports, Neville said: "They came out second half and were just a different team, with urgency. Something sparks them and then all of a sudden they come alive.
"They can't keep doing that, because when fans are in the stadium, if teams like Spurs get in front of them, with the fans behind them, they won't be allowed to be as insipid as they were in the second half, Spurs.
"I think they've got to sort it out, Manchester United. But if you're looking for character in a football side: winning away from home, winning from behind, winning when you're not playing well, being good on set-pieces, those things that define resilience and good character, they're the things you look at, and this United team have it in abundance at the moment.
"Second half they were breathtaking at times, and some of the football was brilliant."
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The result saw United open up a seven-point gap between themselves and third placed Leicester, and they now look almost certain to finish in the runners-up spot this season.
Next they turn their attentions back to Europa League duties, however, as they attempt to ensure a smooth progression to the semi-finals when they face Granada in the second leg of their last-eight clash on Thursday holding a 2-0 advantage.