In return for the 2006 Nats' 1st Round pick, the Rangers sent both infielder Chris Bostick and right-handed reliever Abel De Los Santos to the Nationals.
De Los Santos, who pitched at A-ball in the Rangers' system in 2014, started the year at Double-A in the Nationals' organization and got a surprising call to the majors in July.
"[Abel] De Los Santos is a starter-made-reliever and since he's gone to the bullpen his velocity and stuff has spiked," Rizzo said last winter. "He had a terrific year last year and we think that he'll come really quickly."
Before De Los Santos made his sort-of-surprising MLB debut, now-former Nats' skipper Matt Williams talked to reporters about not being all that familiar with the 22-year-old righty.
"We don't know a lot because he's new to the organization this year," Williams said. "We didn't get a chance to see him in Spring Training, but we certainly have reports from everybody that's seen him within the system.
"He's been closing some games for [Harrisburg], pitching high-leverage situations and back-of-the-bullpen situations for them. Everybody loves his stuff. He's got good stuff, throws strikes and has got a breaking ball to go along with it that he can spot when he needs to, so he's been doing well."
De Los Santos made just two appearances in the majors.
Over 39 games and 57 ⅔ innings pitched at Double-A Harrisburg in the Nationals' system, the reliever was (4-4) with eight saves, a 3.43 ERA, 3.39 FIP, 12 walks (1.87 BB/9) and 55 Ks (8.58 K/9).
Once the season ended, De Los Santos was sent to the Arizona Fall League, where he's (0-1) with ten hits, nine runs and a walk allowed in four innings.
Earlier this week, the right-hander was named as the Nationals' lone representative for the 2015 AFL Fall Stars Game.
The 10th annual AFL Fall Stars Game takes place on Saturday November 7th at 8:00 PM EDT. It will be broadcast on the MLB Network.