AceShowbiz - Rockers Sum 41 have pulled out of the Vans Warped Tour to allow injured frontman Deryck Whibley to recover after he was attacked in a bar brawl. Whibley was hospitalized after three men reportedly assaulted him during a night out in Japan last week. The attack is believed to have aggravated a previous back injury from 2007.

The star played through the pain as Sum 41 performed at a Japanese festival two days after the incident but his condition has not yet improved - and the "Fat Lip" hitmakers have decided to cancel their five remaining dates on the rock tour so he can rest.

A statement from the band reads: "Knowing that they are unable to deliver their signature high energy show, Sum 41 made the tough decision that a break is needed while Deryck begins rehabilitation for the slipped disc. (He) is expected to make a full recovery with the necessary treatment and rest."

Drummer Steve Jocz adds, "(We) are very disappointed that we have to pull off the tour. (But) we know that it would be more frustrating for the fans if we can't give it our all. Deryck is doing everything he can to get himself better and we're there for him."

The Canadian rockers hope to continue their world trek in Europe at the end of the month.