Dickey threw five scoreless innings and allowed just one hit against the Giants on Thursday. He was 1-0 with a 2.25 ERA in seven Spring Training games.
"I pitched as well as anybody," Dickey said. "I pitched as well as I can pitch. I felt good about what I did. Thursday night I thought I pitched real well. It's part of the business. It's real unfortunate.
"They said it was a hard decision and all of that. I would like to believe what they say. There is no reason not to believe them, which is nice. You don't always get that in baseball. I'm choosing to believe what they say. Again, I felt I've proved myself enough where they shouldn't hesitate [to keep me]."
Dickey had to clear waivers before the trade was finalized.
"It is late and rosters are crowded, so as far as getting picked up on waivers, sometimes that's hard at this point." Dickey said. "Minnesota, obviously, wanted me back, or they wouldn't have had to trade a player. I thought I'd probably end up back there. I didn't know in what capacity."
The Mariners opted to go with an 11-man staff with a six-man bullpen instead of seven, and Dickey, who has an option left, was the odd man out.
"We had been talking to [the Twins] for a few days before we had to offer him back," Mariners general manager Bill Bavasi said. "Until we gave them a group of names last night, I thought they weren't going to do anything. I thought he would go back if he didn't make our team. They came back with a few names today, and one was acceptable."
The 'pen will consist of Cha Seung Baek, Ryan Rowland-Smith, Eric O'Flaherty, Sean Green, Mark Lowe and closer J.J. Putz.
"We feel like our starters are in good shape," Mariners manager John McLaren said of going with a six-man bullpen. "We feel like they can go deep in the game. We feel like we've got an insurance policy in Triple-A in Dickey. That gives us some inventory."
By going with 11 pitchers, it allowed the Mariners to keep both Mike Morse and Charlton Jimerson as extra position players.
The Mariners also optioned outfielder Greg Norton to Triple-A to Tacoma.