The Utah Jazz have locked up at least one of their big men.

The Utah Jazz and center Mehmet Okur have agreed in principle to a two-year contract extension worth just under $21 million, according to NBA front-office sources.

Okur could have been a free agent this summer but elected on June 30 to complete the final season on his current contract with the Jazz at $9 million.

Sources told ESPN.com that Okur and the Jazz have quickly reached terms to extend the contract by two more seasons at $20.8 million starting in 2010-11.

I pegged Okur’s value at about $8-$9 million per season, but like most of my estimates, I bought into the idea that teams were going to be more frugal this offseason. Okur is a 6’11” face up center who averaged 17.0 points and 7.7 rebounds this season. He also has terrific range for a big man, nailing almost 45% of his three point attempts. He’s not a factor on help defense, but with his girth he’s pretty good one-on-one in the post.

Paul Millsap is a restricted free agent, but hasn’t yet signed an offer sheet with another team. Carlos Boozer elected to play one more year in Utah, but there is talk that he may be headed to Chicago as part of a three-team trade involving Kirk Hinrich and Tyrus Thomas. If Utah pulls the trigger, they’d be building around a core of Deron Williams, Ronnie Brewer, Thomas, Millsap and Okur. It doesn’t make much sense to keep both Boozer and Millsap around, as they are very similar players. It seems the Jazz feel that Millsap is the better value, but would like to get something in return for Boozer. Thomas wouldn’t represent equal value, but it’s tough to get equal value these days.