The 31-year-old Ziegler is 3-2 with a 2.39 ERA and one save in 43 appearances and 37 2/3 innings. He will join an Arizona team hoping to challenge the World Series champion Giants in the NL West race. The surprising Diamondbacks entered Sunday three games behind San Francisco.
"We're trying to get better and trying to make the bullpen better," manager Kirk Gibson said before the Diamondbacks played the Dodgers in Los Angeles. "I think you're seeing an effort by the organization to try and let us continue to do what we've done and go beyond what we've done. So that part of it energizes you."
Diamondbacks general manager Kevin Towers made revamping Arizona's bullpen, the worst in baseball last season, a priority when he was hired in September. Their relievers entered Sunday with a cumulative 3.46 ERA since the All-Star break.
The acquisition of Ziegler was the second big move by Arizona leading up to the 4 p.m. EDT non-waiver trade deadline Sunday. They got starter Jason Marquis from Washington on Saturday.
"We all know that K.T. is a guy who's aggressive, but aggressively smart, and he just proved that," closer J.J. Putz said. "It says that we expect to keep doing what we're doing."
Parting with Allen was difficult for Gibson -- and not because the trade left him without a backup first baseman on Sunday.
"Brandon's a quality guy," Gibson said. "I'll always have a good affection for Brandon, the way he approached his job. He's a tough kid, a good kid and a hard worker. We wish him well, and he'll do well. He'll be around a long time."
"We had talks. We were close to consummating the deal," Beane said after Sunday's 7-3 win over Minnesota while declining to go into further detail.
Ziegler, the lanky right-hander with the sidearm delivery that has done him well so far, tied the major league mark for relievers by pitching 39 straight shutout innings to start his career in 2008.
The 6-foot-4 Ziegler is durable. He's made 223 appearances in four years and has never been on the disabled list.
"I'm thankful to the A's for the opportunity they gave me, but I'm really excited to be moving to a team in a pennant race. Every player's dream is to win a World Series title and I hope I can help Arizona accomplish that," Ziegler told the AP in a text message.
Ziegler received a $1.25 million, one-year contract in January to avoid salary arbitration. He was part of an A's pitching staff that last year led the AL in ERA (3.56) and shutouts (17) while holding opponents to a .245 batting average.
"He'll definitely help the bullpen," Putz said. "He's a guy that can pitch in many different situations, and he kills righties. He just gives Gibby another weapon to mix and match to get to David (Hernandez) and myself, so it's a good move."
The 25-year-old Allen batted .306 with 18 homers and 66 RBIs for Triple-A Reno. Three of his five hits in 11 games with the Diamondbacks this season are homers, one of which traveled an estimated 455 feet on July 19 at Chase Field against Milwaukee. But he's hitting only .172, and struck out his final two times up with the Diamondbacks in Saturday's 6-4 win.
"It's the deadline, so there was a lot of talking going around. But I hadn't heard anything about myself, so it's a little shocking," Allen said. "I had a good opportunity here, and hopefully I can take advantage if I can get an opportunity over there and do well. The only way to look at it is that somebody wants you and appreciates what you can offer."
Norberto, 24, appeared in 33 games with the Diamondbacks last season and was 0-2 with a 5.85 ERA. He is 6-2 with a 4.25 ERA and one save for Reno this year.