Padraig Harrington is almost a certainty for Europe's Ryder Cup team
Padraig Harrington has withdrawn from next month's Celtic Manor Wales Open to undergo keyhole surgery on his knee.
The three-time major champion will play this week's PGA Championship at Wentworth before having the procedure which will keep him out for two weeks.
The Irishman will then be fit to play the US Open at Pebble Beach on 17 June.
"There seems to be some floating cartilage around there and if I don't get it out I'm going to have arthritic problems," Harrington, 38, said.
"It is something that has to be done sooner rather than later and the doctor confirmed he wanted to get in there so it does not cause me any more problems so unfortunately it means I lose one event.
He announced on 6 May he would be attending the event at Newport, then he confirmed his withdrawal on Tuesday.
"I would have liked to play at the Wales Open as I like the golf course and I think I can be competitive there but such is life, I must look after my health and it means getting this done."
Ryder Cup star and world number 18 Luke Donald is now the only big name player set for the Celtic Manor tournament, starting on 3 June.
This year's Wales Open will be played on the Twenty Ten course which will be used for October's Ryder Cup
European captain Colin Montgomerie had been keen for potential team members to enter the Wales Open and Harrington - currently fourth on the points list for the European team - is almost a certainty to face the USA.
Englishman Donald, who has finished in the top five in three major tournaments, confirmed he would make his debut in the Wales Open as he seeks to star in his third successive Ryder Cup.
"Hopefully it will be good practice for the Ryder Cup... I'm determined to make the team again," said Donald, currently seventh on the world points list.
The top four on the world points list, plus the top five on the European points list not otherwise qualified from the world points list will qualify for the team.
Captain Montgomerie also has three wild-card selections to complete his 12-man team to face holders the USA.
Donald was unavailable for the last match at Valhalla in 2008 because of a wrist injury, but contributed five-and-a-half points from a possible seven in the 2004 and 2006 events.
Graeme McDowell and Oliver Wilson, two members of the 2008 European team, have also signed up for this year's Wales Open, which has a £1.8m total prize fund.
Germany's Martin Kaymer, now 11th in the world rankings, is also thought to be considering entering.
However, leading European lights Lee Westwood, Rory McIlroy, Ian Poulter, Sergio Garcia and Paul Casey have other commitments.
Jeppe Huldahl won last year's Wales Open with a nine-under-par total.
Other past champions include Ryder Cup stars Robert Karlsson, Miguel Angel Jiménez, Ian Poulter, Paul McGinley and Paul Lawrie.
The 2010 winner will pocket £300,000 as well as having had the chance to impress Montgomerie ahead of the Ryder Cup.
Wales' latest European Tour winner Rhys Davies will spearhead an in-form Welsh challenge hoping to produce the first home winner.
Davies captured his maiden European Tour triumph at the Trophée Hassan II in Morocco in March and has risen to become Wales' number one ranked golfer during his rookie season.
The 24-year-old will be joined by fellow Welshmen Stephen Dodd, Jamie Donaldson, two-time European Tour winner Bradley Dredge and former Ryder Cup star Phil Price in a strong Welsh assault on the 11th Welsh title.