UPDATE 1-Soccer-Injured Messi to miss 'clasico' against Real

(Updates with confirmation and quotes)

MADRID, Dec 15 (Reuters) - Barcelona forward Lionel Messi will miss the 'clasico' against Real Madrid next weekend after picking up a thigh injury in Saturday's 3-0 win at Valencia.

The Argentina international pulled up in the 42nd minute holding his left thigh and was substituted soon after.

The club's initial diagnosis was that he had torn a muscle and would be out of action for about a month.

"It's the worst thing that could happen to Barcelona. He is a player who can turn a game and is in form. We hope he recovers as soon as possible," sports director Txiki Begiristain told the club's Web site (www.fcbarcelona.com).

"It's bad news for him and for the team," coach Frank Rijkaard said after the game.

The 20-year-old is Barca's leading scorer in the Primera Liga with eight goals. Second-placed Barca host arch-rivals and league leaders Real at the Nou Camp next Sunday. (Reporting by Mark Elkington)