Former Manchester United forward Robin van Persie has told Alexis Sanchez to "find a way to be happy again" in order to kick on at Old Trafford.

Sanchez has only scored five times in 45 appearances for the Red Devils since a switch from Arsenal midway through the 2017-18 campaign.

The Chile international continues to be linked with a move away from the 20-time English champions, although the attacker's astronomical wages could ultimately see him remain in Manchester.

Van Persie inspired United to the 2012-13 Premier League title during his time at the club, and the Dutchman has claimed that Sanchez's unhappiness has played a huge role in the South American's struggles.

"He is still a wonderful player, still a great player. He needs to find a way to be happy again," Van Persie told Goal.com. "If you are happy, you want to create and have fun. He had that in his first couple of months from what I saw and he needs to find that again.

"He can still play, he is still a fantastic football player. He just doesn't really look happy and the reason why this is... I don't know. I can only guess, but from distance, he looks unhappy and he needs to find a way to be happy again."

Sanchez did not play a minute of United's pre-season after picking up a hamstring injury during Chile's Copa America campaign, while he was not involved against Chelsea last weekend.