Hernandez, who was caught off guard by the deal, joins an Arizona team that enters play Monday tied for second with the Dodgers just two games behind the National League West-leading Padres. The Dodgers, who made a couple of deals in July, have won nine straight.
"It's a surprise," he said. "It happened and I have to deal with it. I found out in the morning when [Nationals general manager Jim Bowden] called me. I have to go [to Arizona] and work. I'm playing on a different team."
"He's a perfect fit," D-Backs manager Bob Melvin said. "No. 1, he's been on the big stage before and pitched well in big games. No. 2, he's an innings eater and that's something we really needed. I don't see how we could have found a better fit for what we needed. It shows the players that we are taking care of what was a deficiency. If there was an area we needed to strengthen, [the rotation] was it."
Melvin declined to say where Hernandez would fit in the rotation, saying he would wait until at least Tuesday to announce which starter would be taken out of the rotation. In addition, the D-Backs will need to make a roster move to clear a spot for Hernandez once he joins the team, which is expected to be Wednesday.
Because he pitched Sunday against the Padres, Hernandez would next be available to pitch Friday, but whether he starts that day or Saturday will depend in part on how Brandon Webb responds after a throwing a bullpen session Tuesday.
The D-Backs rotation, after Webb and Miguel Batista, has been an enigma throughout the year. Juan Cruz, Claudio Vargas and Enrique Gonzalez at times pitched very well and at other times were unable to work deep into games, putting a strain on the bullpen.
Then this past week, Webb missed a start with stiffness in the forearm area just below the elbow. Though the club feels the injury is not serious, it certainly increased the urgency for the team to add a starter.
"We've worked hard to get to the point where we have a chance," Byrnes said. "We wanted to do everything we could, balancing the short-term with the long-term, to try and take advantage of that."
Hernandez, 31, is 9-8 with a 5.34 ERA this season, but has pitched better in the second half, posting a 3-0 record with a 3.27 ERA since the All-Star Game. He is known as a workhorse, having thrown at least 200 innings in each of the last six seasons and 199 2/3 frames in 1999. His 31 complete games since the start of the 2000 season are the most in baseball.
Also attractive to the D-Backs is the fact that Hernandez has pitched well in the postseason. In 1997, he helped lead the Marlins to the championship and was named the Most Valuable Player of both the NL Championship Series and the World Series. Hernandez has a 6-2 postseason record with both losses coming with the Giants in 2002.
"This is a guy that has a chance to give us a real shot in the arm," Byrnes said.
Hernandez has won his last four decisions and pitched well Sunday against the Padres, allowing two runs over seven innings. The D-Backs, though, had interest in Hernandez before that, having claimed him on waivers last week and being informed that they had been awarded the claim Thursday.
That mean they had until Monday to strike a deal with the Nationals.
"It helped," Byrnes said of the fact that Hernandez had pitched well of late. "This is a guy that had a very good career and a long track record, but to see him pitch a few good games in a row was helpful."
The D-Backs had to part with two good pitching prospects in right-hander Garrett Mock and lefty Matt Chico. Both were third-round draft picks, Mock in 2004 and Chico in 2003.
Mock was 4-8 with a 4.95 ERA for Double-A Tennessee while Chico was 7-2 with a 2.22 ERA in 13 starts for Tennessee after being promoted from Class A ball earlier this year.
"You have to give up something to get something," Byrnes said.
The D-Backs were likely willing to part with prospects they liked because Hernandez's contract runs through next year, when he is due to earn $7 million. The Nationals included just under $2 million in the deal, which will cover most of Hernandez's salary for the rest of this season.
Hernandez's half-brother, Orlando "El Duque" Hernandez, made nine starts for the D-Backs earlier this year before being dealt to the Mets in exchange for Jorge Julio.