Morse was acquired by the Mariners along with Miguel Olivo and Jeremy Reed for Freddy Garcia and Ben Davis on June 27, 2004.
Beginning the 2005 season with the Triple-A Tacoma Rainiers, he made his major league debut on May 31, 2005.
Although Morse made it to the big leagues as a shortstop, with the arrival of Yuniesky Betancourt, Morse began to develop as a utility player, having spent time at first base and left field.
In 2005, he was suspended for 10 days for using performance-enhancing drugs.

On July 6, 2006, Morse had surgery to repair a torn medial meniscus of his right knee.
In 2008, Morse had the best batting average in the major leagues in spring training, batting .492.
After playing only 5 games in 2008, Morse suffered a torn labrum diving for a ball in a game against the Los Angeles Angels of Anaheim; he had surgery to repair it and missed the rest of the season.

On April 1, 2009, Morse cleared waivers and was sent outright to the Mariners' AAA club, the Tacoma Rainiers.
Morse was acquired by the Mariners along with Miguel Olivo and Jeremy Reed for Freddy Garcia and Ben Davis on June 27, 2004. Beginning the 2005 season with the Triple-A Tacoma Rainiers, he made his major league debut on May 31, 2005. Although Morse made it to the big leagues as a shortstop, with the arrival of Yuniesky Betancourt, Morse began to develop as a utility player, having spent time at first base and left field. In 2005, he was suspended for 10 days for using performance-enhancing drugs.
On July 6, 2006, Morse had surgery to repair a torn medial meniscus of his right knee. In 2008, Morse had the best batting average in the major leagues in spring training, batting .492. After playing only 5 games in 2008, Morse suffered a torn labrum diving for a ball in a game against the Los Angeles Angels of Anaheim; he had surgery to repair it and missed the rest of the season.
On April 1, 2009, Morse cleared waivers and was sent outright to the Mariners' AAA club, the Tacoma Rainiers.
Michael Morse