Updated

In a trade between struggling teams in the Western Conference, the Colorado Avalanche acquired former No. 1 pick Erik Johnson and Jay McClement from the St. Louis Blues for Chris Stewart and Kevin Shattenkirk.

The Avs, who have dropped nine straight entering Saturday night's game with San Jose, also receive a first-round pick in 2011 or 2012. Colorado surrenders a conditional second-round selection in 2011 or 2012 in the deal announced early Saturday.

Both teams also swung deals Friday as they shake up their rosters.

Colorado exchanged one struggling goaltender for another, acquiring Brian Elliott from the Ottawa Senators for Craig Anderson. The Blues sent defenseman Eric Brewer to the Tampa Bay Lightning for defenseman Brock Beukeboom, an unsigned draft pick, and a third-round pick in 2011.

The 6-foot-4 Johnson was the top overall pick in 2006. A rugged defenseman, he has five goals and 14 assists in 55 games this season. Johnson also helped the U.S. to a silver medal at the 2010 Vancouver Games.

"We are excited to be adding a top young defenseman in this league, a player who will have an impact on our blue line for several years to come," Avs general manager Greg Sherman said in a statement.

McClement has spent his entire career with the Blues organization, playing in 449 games. The 27-year-old forward has six goals and 10 assists this season in 56 games.

"Jay McClement brings six years of NHL experience and will compliment our young hockey club. He will also have an important role on our penalty killing unit," Sherman said.

Stewart was regarded as one of the cornerstones of Colorado's youth movement. The Avalanche signed him to a two-year deal last September after he scored a team-leading 28 goals in 2009-10.

But the 23-year-old forward has been hampered this season after breaking his left hand Nov. 27 in a skirmish with Minnesota's Kyle Brodziak. Stewart missed 21 games and hasn't been the same since his return on Jan. 14, scoring just two goals.

Shattenkirk made his debut on Nov. 4 against Vancouver. He became just the second rookie defenseman in NHL history to reel off a points streak of nine or more games, joining Barry Beck, who had two 10-game streaks while with the Colorado Rockies during the 1977-78 season.

The 22-year-old Shattenkirk was a first-round pick of the Avs in 2007. He has seven goals and 19 assists this season. He also was invited to take part in the skills competition during All-Star weekend.

"We're very excited to acquire a young emerging power forward in Chris Stewart and a top young NHL defenseman in Kevin Shattenkirk," Blues general manager Doug Armstrong said on the team's website. "These are two solid young players which will help us now and continue to grow and improve our team."