"We have a lot of lefties coming up and obviously it gives us a little better balance," McClendon said prior to Friday's game. "He had a good spring, he's been playing well down there. We're just trying to balance out that lineup a little more."
The 29-year-old hit .433 with seven RBIs in 17 Cactus League games, but was sent down when the Mariners opted to go with youngsters Abraham Almonte and Stefen Romero along with veterans Corey Hart, Michael Saunders and Ackley in their original outfield group.
But Hart has played mostly a designated hitter, leaving Romero and the switch-hitting Almonte as the only right-handed outfield options. With the team looking to get regular playing time for Nick Franklin, the 22-year-old infielder was sent down and Gillespie got the call.
"He swung the bat extremely well this spring," McClendon said. "The numbers caught him a little bit and we just didn't have the room. Right now we're trying to play with the roster and get the right fit. This guy was swinging the bat well down there, so hopefully he'll continue to stay hot up here."
Gillespie has had brief Major League stints with the D-backs, Giants and Cubs over the past four years, hitting .225 in 78 games. He signed a Minor League deal with Seattle in January.
"When I signed, the roster was pretty left-hand oriented," Gillespie said. "I knew talking with them they'd probably go out and try to get some right-handed bats, but at the same time I felt this was going to be a good spot for me. Being from the Northwest and growing up in Portland, all things being equal with another team, I was going to choose the Mariners. So far it's working out."
Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB as well as his Mariners Musings blog. This story was not subject to the approval of Major League Baseball or its clubs.