Blues forward Robby Fabbri has a torn left anterior cruciate ligament and is out for the season.
The Blues have recalled Kenny Agostino and Magnus Paajarvi from Chicago.
The Blues said Fabbri is expected to be ready to play by the start of training camp next season.
Fabbri, among the team leaders in scoring, was hurt when he was checked into the boards in front of the Blues' bench with 11:18 to go in the first period on Saturday by Pittsburgh's Carter Rowney. Fabbri was skating up ice and had just let go of the puck when hit, and made contact with the left side of his body. He went to ground, briefly reaching around his knee as he fell on his back before rolling over on to his knees and staying there.
He did not get up quickly and when he did, he put no pressure on his left leg as he left the ice and was helped down the hallway.
Fabbri is tied for fourth on the team in goals with 11, though his performance has been streaky. He went 12 games without scoring to start the season, then had 11 in his next 23 games. He went into Saturday's game without a goal in 15 games.
But there were encouraging signs in his game. After not putting a shot toward the net, on target or off, against Minnesota in the last game before the All-Star break, he had six shots on goal against Winnipeg and three against Toronto. In his 2:05 of ice time before the injury on Saturday, his one shot attempt was blocked.
As a 19-year-old rookie, Fabbri had 18 goals and 19 assists, and his quick start to the season made it an easy call for the team as to whether to keep him or send him back to juniors.
The team leaves on Sunday for a game in Philadelphia on Monday.
The Blues have been relatively blessed when it comes to injuries this season. They've lost among the fewest games to injury in the league and the players they've lost have mostly been those in supporting roles. Among the team's top players, only Alexander Steen, who missed six games, and Jaden Schwartz, who missed four, have missed multiple games.
Agostino leads the AHL overall with 60 points, including 42 assists through 48 games. He was originally signed by the Blues as a free agent in the offseason and was one of the last players cut from camp. He's played in 10 NHL games, all with the Calgary Flames.
Paajarvi has six goals and 10 assists in 25 games with the Wolves this season. (He missed 18 games due to injury.) He made the Blues squad out of training camp and scored in the season opener, but was sent back to the minors when Jori Lehtera came off injured reserve. The Blues chose to send Paajarvi down instead of Ty Rattie because the Blues thought Paajarvi would pass through waivers but Rattie wouldn't.
Paajarvi has been up and down with the Blues several times. He's played in 279 NHL games, with 36 goals and 45 assists.
In addition to Paajarvi and Agostino, the Blues also have Dmitrij Jaskin available. He's been in and out of the lineup all season, most recently out as the team has gone with Nail Yakupov.
