PORTLAND, Ore. - Trail Blazers center Greg Oden, the No. 1 pick in the NBA draft, will undergo exploratory arthroscopic surgery this week because of pain in his right knee. An MRI taken last week showed Oden may have some cartilage problems, general manager Kevin Pritchard said Monday.

Greg Oden waves to several thousand cheering Portland Trail Blazers fans during a rally in Portland, Ore. in this June 29, 2007 file photo. Oden, the No. 1 pick in the NBA draft, will undergo exploratory arthroscopic surgery this week because of pain in his right knee. (AP Photo/Don Ryan)

A timetable for Oden's return will be set following the surgery, which will take place Thursday in Vancouver, Wash. The Trail Blazers open training camp in three weeks, and the regular season starts Oct. 30.

This is Oden's second health problem since the Trail Blazers drafted him in June. He had a tonsillectomy in July after struggling in two Las Vegas summer league games.

Oden recovered from that operation and was working out in the Portland area when he felt pain in his knee. The MRI was taken Thursday and Oden refrained from working out over the weekend.

Cheri Hanson, a team spokeswoman, said Oden and Trail Blazers coach Nate McMillan wouldn't be available to answer questions. Efforts to reach Oden's agent, Mike Conley Sr., by phone weren't successful.

Oden, despite being hampered by a wrist injury, averaged 15.7 points and 9.6 rebounds for Ohio State last season, leading the Buckeyes to the national championship game as a freshman. He had 25 points and 12 rebounds in the loss to Florida.