Sep 01, 2009 2:43 PM EST

Dustin Ackley took batting practice at Safeco Field for the first time on Monday.

"That first swing, I didn't know where the ball was going to go or if I was even going to hit it," said Ackley. "It was a relief."

Ackley was in Seattle to officially sign his five-year major-league deal with the Mariners, worth at least $7.5 million.

Ackley was the number two overall pick in the 2009 MLB Draft.

Via Seattle Times