Former Netherlands captain Ruud Krol believes it's obvious Robin van Persie is unsettled at Manchester United.
Goal reported on December 14 that Van Persie was considering his future with the Premier League champions as he continued to be disillusioned with life under manager David Moyes.
The Dutch striker has been criticized for his anonymous performance in the Champions League defeat to Olympiakos on Tuesday, where the 30-year-old missed a crucial chance to halve the deficit late on in Greece.
Van Persie's frustration at the first-leg loss boiled over into his post-match comments, with the Dutchman insisting his teammates make it difficult for him by taking up his space in games, while he also claimed that United has endured a "lousy" 2013-14 campaign.
Krol, who appeared 83 times for his country, believes that the former Arsenal star is showing signs that he is not comfortable at Old Trafford.
"I watched him play against Olympiakos the other night in the Champions League and he failed to put away a chance that he would normally score blindfolded," he told Goal. "Then his reaction later spoke volumes. He is not settled - actually the whole team is lacking self-belief.
"Nobody doubts the player's qualities or what he can do with the ball. Such crisis moments occur once in a while, but Van Persie will definitely come good. Holland needs him for the World Cup."
Van Persie is contracted to United until 2016, having joined from Arsenal for 24 million pounds back in 2012, and has scored 14 goals in all competitions for the Red Devils this season.