Justin Upton, left, is restrained by coach Matt Williams after being hit with a pitch against the Washington Nationals during a game on June 5, 2011, in Phoenix. (AP Photo/Arizona Republic, David Kadlubowski)

The Nationals’ aim to repeat as National League East champions seemingly became more difficult yesterday, when the Atlanta Braves traded for Justin Upton in a seven-player deal with the Arizona Diamondbacks.

General Manager Mike Rizzo drafted Upton with the first overall pick in 2005 as the Diamondbacks’ scouting director, and he believes Upton is a great addition for the Braves, who won 94 games last year. But he considered the key player the Braves gave up – utility man Martin Prado – to be just as significant as what they received.

“I haven’t had a chance to digest the whole trade yet,” Rizzo said Thursday evening before he received his Executive of the Year award at the Boston baseball writers dinner. “But Prado is a terrific, terrific baseball player. He’s a different type of contributor than Upton would be. Upton is a terrific player and a guy I’m very familiar with and I love. He’s going to be a good player for them.

“He’s a great player. They had a good team before they got him. They’ve got a good team now. It’s going to be a different team than we’ve seen in the past because Prado is really a thorn in our side. He was always a tough out for us and really one of their most valuable players against us throughout his career.”

Rizzo rightfully called Prado a “pest.” Last season, Prado hit .333/.390/.522 against the Nationals pitching staff. Upton, meantime, went 6 for 21 with two walks, a home run, three doubles and two steals. They may be relieved to see Prado leave the division, but the Nationals have a challenge in store with Upton occupying left field for Atlanta.

>>> Rizzo said the Nationals have not stepped up their pursuit of right-hander Javier Vazquez in an effort to add starting pitching depth, but their interest has not cooled, either. They are still waiting to see if Vazquez will come back after spending the 2012 season in retirement.

“We’ve always been in the monitoring stage,” Rizzo said. “If it’s the right fit for him and the right fit for us, we certainly would have interest because of the talent level he has. … We haven’t got anywhere near [discussing a major or minor league deal]. We’ve evaluated him. We’ve scouted him. We’re going to see, first of all, if he wants to play. After that, we’ll take it from there.”

>>>  The Nationals, Rizzo said, have not made any further progress on a deal to avoid arbitration with right-handed starter Jordan Zimmermann, the lone arbitration-eligible Nationals player yet to sign a 2013 deal. Their talks may still lead to a long-term extension for Zimmermann, but Rizzo is not necessarily bent on locking up Zimmermann.

“We’re talking,” Rizzo said. “We’re in no hurry to do anything like that. We’re in the discussion stage. If it makes sense for him and it makes sense for us, we’ll do something. We have him under control for a long period of time. It’s something we’re both thinking about and going to discuss further.”

Rizzo said the same could be said for shortstop Ian Desmond. While Desmond agreed to a $3.8 million contract for 2013 last week, the Nationals could still kick the tires on signing their shortstop to a long-term deal.

The Nationals control the contractual rights of both Desmond and Zimmermann though the end of the 2015 season.