"It was out of the blue," Hairston said.
Hairston was traded to the Oakland A's after Sunday's 7-6 loss in 13 innings to the Dodgers for two Minor League pitchers, right-handers Ryan Webb and Craig Italiano, as well as a player to be named, also a pitcher.
Webb, 23, will join the Padres in Arizona on Monday. He was 7-1 with a 4.34 ERA over 31 games for the A's Triple-A affiliate in Sacramento. Italiano, 22, was 5-6 with a 5.63 ERA for Class A Stockton. He'll likely join Class A Lake Elsinore.
The Padres sold high on Hairston -- who was hitting .299 with 10 home runs and 29 RBIs -- because, as general manager Kevin Towers said afterward inside an empty clubhouse, "we're looking for some good arms."
"That's the one thing we lack in our system is pitching depth," Towers said, noting the lack of higher-level arms in the system. "We really didn't want to give up Scotty. But for us, this is a move looking beyond this year."
That wasn't anything Hairston wanted to hear. He choked up when talking to reporters, especially when asked about his time in San Diego that began, ironically, in another July trade, this time in 2007 when he was acquired from the D-backs.
"Around this time of year, you're always thinking 'what if.' It happens. I've got to do my job somewhere else," Hairston said. "I came here, they gave me a chance. That's all I can ask. I appreciate that. I'll always remember it.
"It's not something that I wanted. But it doesn't matter what I want. Hopefully, I'll have the same kind of experience over there that I had here."
Hairston hit 35 home runs in 610 at-bats with the Padres and provided protection in the lineup this season for All-Star Adrian Gonzalez (24 home runs). Hairston is hitting .360 against left-handed pitchers. He was making $1.25 million this season.
"Since he's coming here, he's developed into a very good everyday player," Towers said. "This is the first time he's gotten a chance to play on an everyday basis and he's really taken advantage of it.
"He put up good numbers in a tough hitter's ballpark. We really didn't want to give up Scotty. I had a tough time with it last night."
Towers said the deal with the A's came about in the past day, when A's general manager Billy Beane contacted him in the eighth inning of Saturday's game against the Dodgers. Towers had another deal in place, but after talking to Beane, he decided to jump on that deal instead.
"Two big arms," Towers said of Webb and Italiano.
Towers said Italiano throws 95-96 mph and that Webb has "really come into his own this season."
Towers sounded excited about the player to be named in the deal. He said he'll pick from two pitchers sometime this month to determine who it is. Towers said one pitcher has Major League service time. That player could end up the key to the deal.
For the time being, the Padres will use Chase Headley in left field, Tony Gwynn in center field and Will Venable and Kyle Blanks in right. Blanks, who also plays left field and first base, has been taking fly balls in right field the past three days before games.
"These guys are going to get at-bats," Towers said, also mentioning Drew Macias as a possibility for a promotion from Triple-A Portland at some point.