The legendary German midfielder says the fans have a part to play for the Reds.
Boasting a 1-0 aggregate lead, Villarreal travel to Anfield on Thursday as the Liga outfit look to finish the job after Adrian Lopez's last-minute winner gave them the slightest of advantages from El Madrigal last week.
That being said, Liverpool are by no means out of this tie and the club's supporters reminded everybody why Anfield is so special on European nights last month, with the Reds netting three second-half goals to dump Borussia Dortmund out of the competition.
Manager Jurgen Klopp will be hoping for a similar atmosphere tomorrow, and Hamann says that such a setting might be slightly intimidating for the Villarreal players, given their lack of experience on the European stage.
"The crowd will be behind the team and I don't think Villarreal will have faced a crowd like this because it has been a long time since they've been in the Champions League and in the latter stages of a European competition - nerves may set in," he told the club's official site.
"If you look at the stats, it's not actually that much of an advantage playing the second leg at home because I think, in the last four or five years, very few teams who played the second leg at home did go to the final. But I think the physiological factor is probably bigger. When you talk about home advantage, the pitch is no different from over there but the fans can make a big difference because we've seen that against Dortmund.
"I don't think we would have turned the tie around without the fans. When Villarreal walk down the tunnel, I think there might be one or two players who think 'I'm not sure whether I fancy this' - this is what you have to exploit and take advantage of and the fans play a big part in that as always."
Divock Origi, who scored home and away versus Dortmund, will miss the visit of Villarreal, prompting concerns over who will score the goals needed to take them into the final.
Daniel Sturridge started in Sunday's 3-1 defeat by Swansea City, which may suggest Klopp is set to use Roberto Firmino as his spearhead once more.