Manchester United boss Ole Gunnar Solskjaer said he will have to make "tough decisions" when it comes to overhauling his squad this summer.

Per Goal's Sacha Pisani, the Red Devils are expected to invest as they look to close the gap on Liverpool and Manchester City. Meanwhile, a number of players could leave, including Ander Herrera, Juan Mata, Alexis Sanchez, Eric Bailly and more.

Solskjaer said:

"I'm under no illusions that this is not going to be plain sailing; it's going to be hard.

"It's going to be survival of the fittest or survival of the best. That's how ruthless we have to be. We need players here who are going to be able to take us forward.

"That means culture in the dressing room and what we do every single day here to make us challenge again. 

"Liverpool and City are too far ahead at the moment for what we like. We played against a Barcelona team that sets the standard in European football. 

"We're under no illusion it's going to be hard work and there will be some tough decisions made by me, Mike [Phelan] and the club."

The Norwegian added he wants to see players "step up" in the coming weeks with their futures on the line.

United are sixth in the Premier League, 21 points behind leaders Liverpool and 19 back on City, the same margin they finished behind the Sky Blues last season.

The Red Devils lost 1-0 to Barcelona on Wednesday in the first leg of their UEFA Champions League quarter-final.

The sides' lineups offered a stark reminder of the gulf United need to overcome, as Bleacher Report's Rob Blanchette observed:

Football writer Liam Canning wants to see United be more ruthless in moving players on:

As Samuel Luckhurst of the Manchester Evening News noted, they have not always been successful in doing so in recent years:

Clearing out those who are surplus to requirements will be almost as important as bringing in the right players. In terms of recruitment, additions are sorely needed in defence and midfield, as well as on the right wing.