Liverpool's Fernando Torres (R) challenges Olympique Marseille's Ronald Zubar for the ball during their Champions League soccer match in Liverpool, northern England, November 26, 2008.-Xinhua/Reuter

Liverpool is scrutinizing every aspect of how Fernando Torres plays and trains after its record signing was ruled out with a hamstring injury for the third time this season.

The setback, ruling the Spain striker out for up to three weeks, came less than a month into his latest comeback after playing in last Wednesday's Champions League victory over Marseille, and just as the Reds try to break away from Chelsea atop the Premier League.

"It is worrying me because it has happened a few times," said Torres, who was also sidelined twice last season. "After this latest injury the important thing is to recover without rushing a comeback date and trying to make sure it does not happen again."

The 24-year-old Torres had not had any similar muscle or hamstring problems before joining from Atletico Madrid in the 2007 offseason.

Now he is working with Rafa Benitez and his medical staff to discover why his right hamstring is so prone to injury, particularly on international duty.

"The situation is that we have to start again analyzing everything and start with the prevention," Benitez said on Friday. "It's not difficult, it's not one of the worst injuries, but it can happen again and again the same problem so we have to analyze the small things.

"Sometimes it's how you walk, sometimes it's the boots, sometimes it's if you have been doing some exercises before and it is making it worse."

The Liverpool manager insists that Torres, who scored 33 goals in his debut season, was not rushed back after tearing his hamstring during Spain's World Cup qualifying win in Belgium last month.

"It has happened three times with the national team so it is something we have to analyze, we knew maybe they were doing something that is not the best for the player," he said.

Liverpool plays West Ham United at Anfield today.