"People calling for Rafa's head are being very premature," Hamann told BBC Sport. "He has been there five years and has improved them every season.
"Rafa has got everything a top-class manager needs, he will turn it around."
Defeat at Fulham on Saturday means Liverpool are on their worst run for more than 50 years and they face a crucial week in their season as they travel to Lyon in the Champions League on Wednesday and host Birmingham in the Premier League on Monday.
Losing at Lyon would leave Liverpool's hopes of reaching the last 16 in Europe hanging by a thread, while they have already lost five of their 11 league matches this season - including a 3-1 reverse at Fulham on Saturday.
Only Rafa knows how fit players are - it's not for anyone else to judge Dietmar Hamann Ex-Reds star Ronnie Whelan was quoted on Monday as saying "it's all gone wrong with the manager" and Benitez's days at Anfield are "numbered", while former striker Stan Collymore also said the former Valencia coach should be sacked.
But Hamann, who played a pivotal role as a substitute in Liverpool's stunning Champions League victory over AC Milan in Istanbul in 2005, says his former club must stick with Benitez.
"It's almost the first time in his five-year period at Anfield where they've had a bad spell like this," added Hamann. "Every year Rafa has gradually improved Liverpool, every year he has taken them forward.
"There are still another 27 games left in the league and while I don't think they can win it after the start they have made, there is plenty of time to get into that top four.
"The team is good enough to pull through. They were pretty unlucky at Fulham - they could have been ahead at half-time and both the sendings off were harsh, sometimes things just don't go your way.
"But all they need are a couple of good results and a couple of key players to be fit again and once they've won once or twice everything will be fine again."
THE ALAN HANSEN COLUMN Benitez is under pressure - that is a fact, that's not me saying it Whelan heavily criticised Benitez's decision to take star striker Fernando Torres off after 63 minutes of the defeat at Craven Cottage with the score 1-1, but Hamann dismissed the Irishman's comments.
"I don't think you can blame the manager for taking Torres off when he's clearly not 100% fit - maybe Torres asked to be taken off, who knows?" said Hamann.
"It's just ridiculous that people are coming out and saying these things when only the manager knows how fit people are, only he is in charge of that team. I don't think that's up to anyone else to judge.
"I think this game in Lyon on Wednesday is more important than any of the league games they have played recently.
"Financially for Liverpool it is vital for them to reach the last 16 of the Champions League, so at this moment in time you can see why Rafa would prioritise Wednesday's game more than Fulham away.
"There is so much time left in the league - and you saw with Manchester City drawing on Sunday that teams aren't exactly capitalising when Liverpool don't win.
"The big four all lost at least twice in their first 10 games so it seems more competitive at the top and this will work in Liverpool's favour, because you won't need quite as many points as in previous years to get into that top four.
"With Alberto Aquilani getting fit, Steven Gerrard on his way back and the fact that they won't lose any players to the African Cup of Nations in January, I think we'll see Liverpool improving from now on."