|FA Cup fifth round: Chelsea v Manchester United|
|Date: Monday 18 February Time: 19:30 GMT Venue: Stamford Bridge|
|Live coverage on BBC One from 19:00, plus live text commentary and in-play clips on the BBC Sport website and app|
Manchester United interim boss Ole Gunnar Solskjaer says he is confident Alexis Sanchez's form will improve.
Chile forward Sanchez has scored five goals and struggled with injuries since joining from Arsenal in January 2018.
"We know there is a very good player there. It's like the ketchup bottle. When it comes, it comes, and I'm sure he'll be fine," said Solskjaer.
United travel to Chelsea in the fifth round of the FA Cup on Monday, a game which will be shown live on the BBC.
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The most recent of Sanchez's two goals this season came against Arsenal in the fourth round in January.
Signed on a four-and-a-half-year deal reported to be worth £14m a year, the 30-year-old said in an interview with BBC Sport on Saturday that he "would like to have brought more joy to the club".
Sanchez was widely criticised for his performance as a substitute in United's 2-0 home defeat by French champions Paris St-Germain in the Champions League on Tuesday.
Solskjaer won the FA Cup as a player with United in 1999 and 2004. That first cup triumph came four days before the stoppage-time winner from the Norwegian that clinched the Champions League and a historic Treble.
"I'm not going to say it's the last chance [to win a trophy] because we are going to Paris to give it a go - but the chances are slimmer," said Solskjaer before Monday's match at Stamford Bridge.
"Everyone wants to play an FA Cup final. It's one of my best memories playing at Wembley when we beat Newcastle.
"I knew I wasn't going to start the Champions League final, so that was my big moment that season.
"It turned out the other way round but the FA Cup final is something we want to go to."
United are fourth in the Premier League, 14 points behind leaders Manchester City, and face PSG in the second leg of their Champions League last-16 tie on 6 March.
'Chelsea must learn from City's Pep patience'
Chelsea assistant manager Gianfranco Zola has called for patience similar to that given by Manchester City to Pep Guardiola as Blues boss Maurizio Sarri attempts to implement his style of play at Stamford Bridge.
Guardiola's side thrashed Chelsea 6-0 in the Premier League earlier in February - but City finished without a trophy and 15 points behind the Blues in their title-winning 2016-17 season, which was the Spaniard's first in charge of the Etihad Stadium club.
That defeat increased scrutiny on the former Napoli coach's 'Sarri-ball' philosophy - but Italian Zola believes his 60-year-old compatriot simply needs time to "adapt".
"Two years ago, you were probably asking the same questions to Pep Guardiola," said the former Chelsea forward, 52.
"You admire what Pep has done. Certainly he's a good inspiration. Not everything comes together straight away."
"You were asking if he'd keep playing from the back all the time. He said this was not in discussion and part of my game, even in the difficult moment. Maybe he adapted.
"He has adjusted something but not the way he saw football. There are questions about what we're doing but we don't change what we believe is good for this club because, otherwise, we are nothing."