Lambert is heavily tipped to be part of Roy Hodgson’s England squad for this summer’s tournament in Brazil but is currently struggling after what Pochettino described as a knock to his gluteus maximus.
Saints are determined to finish a successful season strongly as they head into fixtures against Swansea at the Liberty Stadium this afternoon and the finale at home to Manchester United a week tomorrow.
Lambert will at best start this afternoon’s match on the bench, with Sam Gallagher likely to get another chance to impress in attack, and Pochettino will not take any unnecessary risks with Lambert now after Hodgson confirmed end of season form will not affect his selections.
“The fact is all players want to play all of the time and that is the case as well with Rickie Lambert,” said Pochettino.
“But if he does have a fitness problem, a physical problem, then it will be unnecessary for us to put him at risk and perhaps give him a greater injury.
“All players have maximum demand to do well and defend this club and they all want to play all the time.
“If we see at the end of the season he is not well then we will reserve him.”
Saints have several injuries heading into today’s game and Pochettino confirmed: “Morgan (Schneiderlin) could make a return. He’s been training well throughout the week but we still need to asses him.
“We also have a doubt about Rickie Lambert and we need to assess him ahead of the game tomorrow.
“We will see maybe if he can come on as a sub or it may be better to not risk him and keep him on the bench.
“He had a knock on his gluteus maximus last week and we need to evaluate whether he will be to take part or not.”
Two other World Cup hopefuls with injury worries are Ramirez and Yoshida.
They hope to earn selection to represent Uruguay and Japan respectively, but are now looking increasingly unlikely to get any game time under their belts before the end of the Premier League season.
“I think they are both going to arrive well at the World Cup and are both going to be fit for the World Cup,” insisted Pochettino.
“The only problem is that we are reaching the end of the season and it might be a bit tight for them to play before the season ends and then head for their national teams.
“They are definitely unavailable for today and we need to assess them ahead of next week’s game but they will have no problems to play with their national teams at the World Cup.”