Wellington, Feb 22 NZPA - New Zealand soccer will hold its collective breath while a leg injury suffered by All Whites captain Ryan Nelsen is assessed this week.

Central defender Nelsen landed awkwardly on his right leg following an aerial challenge during his Blackburn Rovers' 3-0 home defeat of of Bolton in the English Premier League this morning. He appeared to hyper-extend his right knee and lay on the ground grimacing while holding the leg.

After lengthy treatment to what appeared to be his knee, he walked relatively freely and tried to play on before limping from the ground in the 36th minute.

The injury could places Nelsen's place at the World Cup in South Africa in June under a cloud. New Zealand's premier player had been selected to lead the All Whites' in their first game of the year, a friendly against Mexico at Los Angeles on March 4.

Blackburn manager Sam Allardyce was uncertain about the severity of the injury.

"Having only looked at it on the replay I'm hoping that he's twisted his ankle and not his knee," Allardyce told Blackburn's website.

"But he was holding his knee which was the big problem for me. I think it is his one where he's had surgery before, so it'll be 48 hours before we can tell and we'll keep our fingers crossed, not just for us but for him."

Nelsen missed last year's Confederations Cup in South Africa because of a calf injury.

New Zealand coach Ricki Herbert was disappointed to hear of the 33-year-old's injury and had already contacted Blackburn medical staff. He expected to hear a diagnosis within the next two days.

"My fingers will be crossed immensely to hope that the news is good coming out of Blackburn," Herbert told 3 News while travelling to South Africa today on an All Whites management pre-World Cup reconaissance trip.