Red Bull midfielders Luke Sassano and Brian Nielsen had successful surgeries yesterday, and both are expected to miss the rest of the season.

Nielsen had surgery to repair bony cartilage damage in his right knee in a procedure performed by Dr. Riley Williams at the Hospital for Special Surgery. Nielsen, coach Hans Backe and trainer Rick Guter had all told the Post that he had bone-on-bone contact from the previous injury, but that surgery was the last option. Apparently they’ve gotten to that point.

The Danish midfielder, who is already on the DL, will miss five months. Nielsen has played in two games in 2010 after being signed on loan from Vejle Boldklub earlier this season. While his loan expires at the end of December, Backe said the club has the right to sign him outright after that. They’d hoped he could return in time to evaluate him in practice before making that decision, but it is unclear how this surgery changes that timeframe.

Sassano had a right ankle reconstruction procedure, which was performed by Dr. David Levine at the Hospital for Special Surgery. He’ll be out for 4-6 months, but the third-year player _ who has played three games this year _ will be put on the team’s Season-Ending Injury List.