Paul Pogba admitted Manchester United underperformed against West Ham and must improve to have any hope of ousting Barcelona in the Champions League quarter-finals.

United limped to a fortuitous 2-1 win at Old Trafford on Saturday thanks to midfielder Pogba's two penalties either side of half-time.

Felipe Anderson scored in between those goals and West Ham would have taken a late lead had a combination of the crossbar and David de Gea not denied Michail Antonio in quick succession.

The visitors instead left empty handed after Ryan Fredericks' panicked challenge on Anthony Martial allowed Pogba to convert a scarcely deserved winner in the 80th minute.

The result lifted Ole Gunnar Solskjaer's side to within two points of fourth-placed Chelsea in the Premier League and restored a measure of momentum as they seek to overturn a 1-0 first-leg deficit at Camp Nou on Tuesday.

"We didn't have a good performance but the result is there," Pogba told BT Sport.

"It was really open but we didn't play well. With the chances and space we had, maybe we played too slow and weren't dangerous.

"We have to fix that, learn from that and focus on the next one.

"I can't explain if we were tired from the Champions League game. We have to rest now for Tuesday."

Pogba netted the first of his spot-kicks in the 19th minute after eschewing his usual stuttering run-up in favour of a more orthodox approach.

The 26-year-old thinks the change in technique might have helped to get the better of Lukasz Fabianski on two occasions.

"What matters is to put the ball inside the net, that's all," he said.

"Maybe I tricked the goalkeeper, but the most important thing is the three points today.

"I think we had the luck and you always have to take it. Sometime it is for the other team but we took it today."