5:14pm: John Hickey of the Seattle Post-Intelligencer reports that the Mariners have designated infielder Tug Hulett for assignment to make room for Pena on the 40-man roster.
2:15pm: Tom Haudricourt writes that the Mariners have claimed reliever Luis Pena off waivers.
Pena, 26, was designated for assignment when the Brewers claimed Nick Green from the Angels. Brewers general manager Doug Melvin explains:
"It’s like trading Pena for Green," said general manager Doug Melvin. "We needed starters. You hate to give up on a good arm but that was our need."
