"I think it's a pleasant surprise. My intentions and expectations coming into Spring Training were to make an impression," Treinen said. "The fact that I'm still around is an absolute blessing. I can't thank [the Nationals enough] for giving me the opportunity that they have given me so far.
"I'm just trying to make the most of it -- going day by day. Whatever their decision is at the end of Spring Training, it's their decision. I'm doing my absolute best to get myself an opportunity to make an impression with the big club."
Since being in big league camp, Treinen has learned a lot from people in the organization such as Stephen Strasburg, Craig Stammen and pitching coach Steve McCatty.
"It's just a culmination," Treinen said. "They all have little tidbits to give me -- whether it's the mental approach or little tidbits to help me with the couple of things, [like] my breaking ball or changeup. I can't pinpoint one more than the other. Everyone is so willing to help each other. It's your career and you want to perform at your best, but you want other people to do well too."
Treinen, who is rated by MLB.com as the 17th-best prospect in the Nationals' farm system, can throw a sinker as fast as 95 mph.
Treinen, who came from Oakland in the Michael Morse trade in January 2013, is a non-roster invitee. The 25-year-old said coming to the Nationals was the best thing that could have happened to him because of the team's pitching philosophy. As he put it, the Nationals have "taken his career through the roof."
For example, Treinen loves the team's throwing program. He feels he knows his body better because of it.
"Some philosophies [have you throwing] 120 [feet] on a line. Here, it stretches it out every day and you go where your arm feels like it needs to go," Treinen said.
Last season, Treinen played for Class A short-season Auburn and Double-A Harrisburg, and he posted a combined 6-7 record with a 3.47 ERA.
If Treinen is sent down, he will likely start the season as a starter. He said there are pluses to being a starter and reliever.
"I'm open to whatever gives me the best chance to play on the big club," Treinen said. "I've done both in the Minors. I've had downs and ups on both. I can take away positives on both. I'm not opposed to either or -- I just want to do whatever I can to help the club and myself to get there."