Seattle traded for White shortly after the Pirates selected him from the Atlanta Braves' Triple-A roster in the Rule 5 draft.
White, 25, was 5-6 with one save and a 4.40 ERA in 21 games last season with Double-A Mississippi. He was 0-3 with a 6.35 ERA in five starts for the Peoria Javelinas in the Arizona Fall League, which is where the Mariners gained interest in him.
Seattle officials received promising reports regarding White from Peoria's pitching coach, Brad Holman. Holman is the Mariners' Double-A pitching coach.
Players chosen in the Major League portion of the Rule 5 draft must remain in the Major Leagues for the entire 2007 season. If Seattle opts to option White to the Minor Leagues, the club must first offer him back to his original team for $25,000 -- half of the claiming fee of $50,000.
"He gives us some starting depth and another good arm," Mariners general manager Bill Bavasi said.
This means White will likely be in the Mariners' starting pitching mix for Spring Training.
Seattle vice president of player personnel Benny Looper said White -- who played at the University of Washington -- experienced a spike in velocity that put the team on notice.
"He's a big kid [6-foot-4, 215 pounds] with good life on his fastball," Looper said. "We wouldn't have taken him if we didn't think he could help us."
White threw in the 93-mph range during the regular season but was clocked between 91-96 mph in the Arizona Fall League.
White was originally drafted by the Braves in the eighth round of the 2003 First-Year Player Draft. He has compiled a Minor League record of 28-25 with three saves and a 4.00 ERA in 95 games, 63 of which were starts.
Corey Brock is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.