The Nationals selected Ramirez with the sixth pick in the Major League phase of the Rule Five draft last December coming off an impressive run for Ramirez in the Dominican Winter League that was a dramatic step forward for him as I discussed here. He was reportedly throwing in the upper 90s with stats to match.
The Mets will pay the Nationals $25,000 for the right to reclaim Ramirez.
Ramirez missed the entire 2011 season after shoulder surgery. Thus, as Adam Kilgore in the Washington Post tries to explain:
since he spent the entire year on the disabled list the Nationals would have had to keep Ramirez on their 25-man roster all of next season in order to keep him in the organization.
The odds are against Ramirez ever amounting to anything, but when he's right, he throws really hard, so its nice to seem him return to the Mets organization.