The Blues are keeping at least one of their unrestricted free-agent defensemen, re-signing Carlo Colaiacovo to a two-year, $4.25 million contract extension.

The deal will be announced as soon as today. Neither Colaiacovo nor the Blues would comment until the news is official.

Meanwhile on Monday, Blues forward Cam Janssen was one of three eligible restricted free agents on the roster to file for salary arbitration. Goaltender Jaroslav Halak and forward D.J. King did not file.

Restricted free agents Erik Johnson, David Perron and Tyson Strachan, all still unsigned, are not eligible for arbitration this year.

On Thursday, Colaiacovo and fellow veteran defenseman Mike Weaver hit the free-agent market together. Had both found work elsewhere, the Blues would have needed to do one of two things: look for replacements or prepare for a youthful defensive core.

But the re-signing of Colaiacovo, 27, keeps in place at least one veteran, one of the Blues' more offensive-minded blue-liners. Colaiacovo has combined for 61 points over the past two seasons, the most for any defenseman on the team in that span. He has averaged .47 points per game in 130 games with the club.

As a free agent, Colaiacovo attracted interest from a handful of teams, but he kept in touch with the Blues. The club had traded for him in 2008.

"My position hasn't changed in the sense that St. Louis is the first place I want to be," Colaiacovo said last week. "I'm still confident things will work out."

Weaver, 32, remains a free agent, but a source said Monday that both sides are still talking. The veteran defenseman is asking for a three-year extension; the Blues prefer a two-year deal. Weaver recently completed a one-year, $800,000 contract.

The Blues now have eight defensive players expected to return for 2010-11: Colaiacovo, Johnson, Strachan, Eric Brewer, Barret Jackman, Roman Polak, Alex Pietrangelo and Ian Cole.

Russian defenseman Nikita Nikitin, a 2004 draft pick who signed this summer, also will be at training camp.

On another front, Janssen filed for arbitration Monday after trying to work out a contract extension. Scott Norton, the agent for the Blues enforcer, said he still hopes to negotiate a multi-year deal even though the team made a one-year offer to the Eureka native.

"Cam was hoping to keep 'home' home for longer term, but he understands," Norton said Monday. "I'm optimistic we can get something done in an amicable fashion before arbitration. But no one is sure until we put pen to paper."

Enforcers have done well in free agency. Former Minnesota Wild Derek Boogaard signed a four-year, $6.6 million contract with the New York Rangers, a deal averaging $1.65 million per season. Ex-Rangers enforcer Jody Shelley signed a three-year, $3.3 million contract with Philadelphia.

The Blues, however, maintain the rights to Janssen and King, who after playing in a combined 13 games the past two seasons declined arbitration Thursday.

In a somewhat surprising move, Halak likewise did not opt for arbitration despite coming off his best season in the NHL. The Blues goaltender, acquired June 17 from Montreal in a trade for forward prospect Lars Eller, was 26-13-5 with a 2.40 goals-against average and a .924 save percentage in the regular season. He had the fourth-best save percentage (.924) in the playoffs.

Halak, 25, made $775,000 last season with the Canadiens.

On June 23, the Blues made the goalie a qualifying offer of $813,750, which is figured by adding a 5 percent raise to last season's salary. By making a qualifying offer, the Blues retained Halak's rights, allowing them to continue negotiations.

Blues general manager Doug Armstrong and Halak's Los Angeles-based agent, Allan Walsh, were scheduled to talk last week in LA while the team was in town for the NHL draft, but it has not been confirmed whether those negotiations took place.

A source said Monday that Halak didn't file for arbitration because his camp wants to negotiate with the Blues without any deadlines attached.

The Blues have the option of club-elected salary arbitration with Halak. The deadline to file is today at 4 p.m..