NORTHAMPTON, England (AP) — Wales' injury problems have intensified ahead of the Six Nations, with George North the latest player to be a doubt for the start of the tournament.

North's English club, Northampton Saints, says the winger has a knee injury that requires four weeks of rehabilitation.

That timeframe leaves North unlikely to be involved in Wales' opening match, against Scotland in Cardiff on Feb. 3.

Wales coach Warren Gatland has serious injury problems in the back row, with Sam Warburton (knee) missing the entire Six Nations, fellow flanker Dan Lydiate (bicep) also potentially missing, and No. 8 Taulupe Faletau (knee) set to miss the start of the tournament.

Another No. 8, Ross Moriarty, has missed most of the season with a back injury.