The setback, ruling the Spain striker out for up to three weeks, came less than a month into his latest comeback after playing in 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 for 20.3 million pounds (S$47 million).

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 analysing 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. You never know, but I was talking with Torres 10 minutes ago a little and he was thinking about solutions.'

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

'It has happened three times with the national team so it is something we have to analyse, we knew maybe they were doing something that is not the best for the player,' Benitez said. 'With the new staff with the national team there was better communication and it was easier, but after a few weeks we have the problem again so we have to analyse this.'

Benitez said no pressure will be put on Torres to make a swift return, and his absence will give his strike rivals a chance to shine.

'We have Keane and when we bought him it was with the idea that he can score goals. We also have Dirk Kuyt, David Ngog and Ryan Babel,' Benitez said. 'Hopefully they can score enough goals and we can talk about Fernando in three weeks' time.

'We have shown enough quality and character without him and hopefully we can do it again.' -- AP