The 23-year-old left-hander has made some good strides since having shoulder surgery in August 2012, but he needs to continue to show improvement.
How Purke fares for the Arizona Fall League's Mesa Solar Sox will determine where he will pitch in 2014.
So far, so good for the Nationals' third-round pick in the 2011 Draft out of TCU. He's No. 8 on the Nationals' Top 20 Prospects list.
He had a strong effort in his only start of Week 3 in the Arizona Fall League, earning Pitcher of the Week honors.
Purke pitched five shutout innings, giving up just one hit, walking one and striking out three in a no-decision against the Scottsdale Scorpions.
In three starts, he is 2-0 with a 0.00 ERA, three hits allowed, one unearned run, three walks and 12 strikeouts in 12 innings. Opponents were hitting just .079 against him.
"I have been able to command my pitches in the strike zone," said the 6-foot-4, 205-pound Purke. "The guys have been playing very good defense, and we have been swinging the bats well. When that happens, it takes a lot of pressure off you."
Purke said his shoulder feels good. After having surgery to remove bursa sacs and clean up scar tissue, he started back in the spring of 2013, but he wasn't allowed to pitch competitively until late May.
Purke still managed to post a 6-4 record over 18 combined starts between Class A Hagerstown and Class A Advanced Potomac, pitching a combined 90 innings.
"I was two months behind, but I understood the organization's decision about bringing guys along," Purke said. "You don't want to rush back out there and then take a step back.
"They have done a good job with some of their other young guys -- [Stephen] Strasburg, [Jordan] Zimmermann and [Taylor Jordan, all three of whom had Tommy John surgery]. For me, I have been seeing improvements, and I feel good."
Purke was a first-round selection by the Rangers in the 2009 First-Year Player Draft out of high school in Spring, Texas. He had agreed to a $6 million signing bonus, but that was not allowed by Major League Baseball because the Rangers were having financial difficulties at the time.
So Purke went to college at TCU and was 16-0 as a freshman, leading the Horned Frogs to the College World Series. With the shoulder slowing him as a sophomore, the Nationals selected him in the third round of the 2011 Draft, and he signed for $4.4 million.
Purke pitched in the Fall League in 2011 but made only three starts for Hagerstown in 2012 before being shut down. After the 2013 regular season ended, he went to Florida for instructional work to prepare for the Fall League.
It is noteworthy that another player from Spring -- Cleveland Indians outfield prospect Tyler Naquin -- was named the Arizona Fall League Player of the Week during the same week Purke was selected for his honor.
The two know each other well and played against each other in high school and summer ball.
"There were a lot of scouts watching us back then," said Naquin, who plays for the Surprise Saguaros. "He had tremendous stuff, and he continues to impress."
Purke has a good fastball, and he has been working on his sinker in the Fall League.
"If I am in trouble and I need an out, that's the pitch I often go with," he said. "I can induce a lot of ground balls with it."
Purke would like to start as far up the organization's ladder as possible in 2014, and he is trying to be patient.
"I have no clue where I will go. I'll be happy to go where they send me," he said.