10 – Rockies flip Ryan Mattheus to the Nationals (2009)
The Washington Nationals haven’t actually made as many trade deadline moves as you may think since the franchise moved to D.C. before the 2005 season. So this deal for Ryan Mattheus makes the list, as he did end up being a useful player for the Nats.
They traded away Joe Beimel, a left-handed reliever who signed a one year deal with the Nats before the 2009 season. But at mid-season, the team was on its way to a second consecutive 100 loss season, and at the deadline, they were dealing whatever they could.
Beimel had 10 holds in 39.2 innings, while possessing a 3.40 ERA for the Nationals and was bound to make a nice addition for a contender. The Colorado Rockies ended up calling for him and secured his services.
In return, the Nationals got Ryan Mattheus, who became a key part of the bullpen between 2011-2014. They also got Robinson Fabian, but unfortunately, he was never able to make it past High-A.
Back to Mattheus. He never quite consistently worked his way into high-leverage spots, recording just 31 holds in four seasons with the team. But he was useful to have and could get the job done, as evidenced by his 3.60 ERA in that time.
He also holds a little bit of Nationals history too. He was the first Washington Nationals pitcher to record a post-season win since the franchise moved to D.C. in 2005.
He pitched a scoreless seventh inning with a 2-1 deficit against the St Louis Cardinals in game one of the NLDS. Then in the top of the eighth, Tyler Moore came through with a huge two out, two RBI single to put the Nats on top.
Although he does hold that historic moment, overall his Nationals career was distinctly average. But given the lack of deadline trades, he cracks the list at number 10.