Manuel Alminia feels Liverpool are difficult to predict as they are something of a 'Jekyll and Hyde' team.
Arsenal face Liverpool in the second leg of their UEFA Champions League clash on Tuesday, having drawn 1-1 in the first leg last week.
The two sides also played out a 1-1 draw in the Premier League on Saturday and Almunia is expecting another tough game at Anfield.
Liverpool have been in excellent form at home in Europe this season but their fans have also witnessed the occasional disappointment, such as the shock FA Cup defeat to Barnsley.
"They are a bit like Dr Jekyll and Mr Hyde - they change their face," said Almunia.
"Perhaps they are more comfortable playing against more technical teams, I don't know.
"It is difficult to analyse because they are a strong team which likes to fight.
"We are a team which can counter attack well when space is left and make lots of chances. That is our speciality."
Almunia is pleased that Rafa Benitez has had some success at Liverpool, having worked with the Spanish manager at Osasuna at the start of his career.
"I was in the 'B' team at Osasuna when Benitez managed the first team, who were in the second division," he recalled.
"But he did not have a good time in Pamplona - the team was almost relegated and people in the city were not happy.
"He was sacked with five games of the season left. We had to win all of those games to stay up, they put one of the coaches from inside the club in charge and we won them all. It was a miracle.
"So Benitez didn't have success at Osasuna but has gone on to do very well and has proved to be a very good manager."