2000s- Alex Kovalev
Throughout his career, Alex Kovalev was a very productive player before joining the Senators. Kovalev was a key part of the New York Rangers 1994 Stanley Cup championship team and made three All-Star Games.
Prior to the 2009-10 season, the Senators signed Kovalev to a two-year contract hoping he'd be the missing piece to help the Senators go deep in the playoffs after the Senators missed making the 2009 playoffs. Kovalev was a 2009 All-Star, so it made great sense for the Senators to sign him.
Unfortunately in Ottawa, the Kovalev signing was a disaster. While the Senators made the playoffs in 2010, Kovalev had a 16-point drop off from his All-Star season the year prior and finished with 49 points in the 2009-10 season. The Senators were eliminated in six games by the Pittsburgh Penguins in round one.
In the following 2010-11 season, Kovalev's tenure ended after recording 27 points in 54 games as he was traded to the Penguins in February 2011. In the following 2011-12 season, the Senators made the playoffs without Kovalev on the team. Kovalev never lived up to the hype throughout his career before joining the Senators and was a major bust of a free agent signing.