"Motter and Shaffer help us create the depth that is critical to our success," said Mariners general manager Jerry Dipoto. "They are two defensively versatile players who have offensive skill. Shaffer brings power and Motter brings on-base ability and speed. Their additions give us players with Major League experience who allow us to maintain our roster flexibility throughout the season."
Shaffer, 25, played 51 games with the Rays at first base, third base and right field over the past two seasons and put up a .213/.310/.410 line with five home runs and 10 RBIs in 122 at-bats.
Shaffer hit .