Stephen Strasburg moves a step closer to taking the mound at Nationals Park by making his first rehab start Sunday. (Jonathan Newton/WASHINGTON POST)

When he stood on the mound in a minor league stadium last year for the first time since Tommy John surgery, Jordan Zimmermann looked around and saw 500, maybe 600 fans. He had pitched in the majors, and so that should not have meant anything to Zimmermann. But it did. The first thing he noticed was the people.

“You didn’t hear the crickets like you could in Florida,” Zimmermann said.

Sunday, at Class A Hagerstown, Stephen Strasburg will pitch in his first competitive game since Aug. 21 last year, the night he threw a 91-mph change-up to Domonic Brown in Philadelphia and snapped the ulnar collateral ligament in his right elbow. Strasburg has finished his sweltering, lonely, laborious rehab in Viera, Fla. Only a month or so of minor league rehab starts separate him from the major leagues, a final stage of recovery that begins now.

Strasburg has already been throwing simulated games — intermittently pitching to several batters and resting to replicate the break between innings — for the past month. He has thrown his full range of pitches with full ferocity, surpassing 95 mph with his fastball.

But the controlled environment the Washington Nationals created for those sessions will cede Sunday to a normal game, against opponents who have little regard for the fitness of Strasburg’s right elbow and in front of thousands of fans. Zimmermann experienced the same process last season, and for him it meant pitching before more than a dozen people. It also meant the end of a yearlong recovery was almost near.

“I knew once I started my rehab games, time would fly,” Zimmermann said. “I was getting that much closer to being big league ready.”

The best part for Zimmermann may have been saying good-bye to his apartment in Viera, the home of the Nationals’ spring training facility and Gulf Coast League affiliate. “It’s good to get out of Florida, that’s for sure,” Zimmermann said. “It’s hot, miserable.”

When Zimmermann moved on from Florida, he left any trepidation about the health of his elbow behind. Throwing in simulated games eased his mind and convinced him he had fully healed from the surgery.

“As soon as I left Florida, I knew I was fine,” Zimmermann said. “The first couple sim games in Florida is when I really let it go. It didn’t hurt after that, so I knew it was pretty much good to go.”

Still, the competitive atmosphere altered the stakes. Nationals coaches and officials can manage every detail of a simulated game, which about 10 people watch. Strasburg may be the main attraction in a sold-out stadium packed with nearly 7,000 people, but he, like every other player on the field, will be at the mercy of the course of the game.

“There’s definitely some apprehension, that’s for sure,” said Paul Menhart, who oversaw Zimmermann’s first rehab start last year as Potomac’s pitching coach. “You rehab down in Florida, and it’s so controlled. You’ve got anybody and everybody watching every move you make. There’s really nothing at stake except for the way you feel.”

Zimmermann used the simulated games to finish building arm strength and stamina, and to gain confidence in his reconstructed elbow. But even though those “games” included throwing to batters, Zimmermann did not pitch as he would have before the injury.

In Florida, Zimmermann fired his pitches over the plate without much thought of commanding them. He did not concern himself with hitting corners or sequencing pitches. He just wanted to get used to throwing in the general vicinity of a strike zone with a hitter standing in the box.

Once his minor league rehab began, that changed. Zimmermann had worked for almost a year to rebuild the process of throwing like a pitcher. In the minors, he would rebuild the process of thinking like one. In his first rehab start, the subtleties of pitching began coming back to Zimmermann. He studied swings of hitters to think about his next pitch. He moved the ball in and out, up and down.

“I couldn’t just throw stuff over the middle,” Zimmermann said. “I had to work both sides of the plate and start to learn how to pitch again. That was a big process.”

While Strasburg will begin in low-Class A Hagerstown, Zimmermann started in high-A Potomac. He pitched two innings in his first start, the same workload Strasburg is expected to pitch. Zimmermann had a sparkling debut, allowing no runs. But the Nationals will be worried primarily about something beside Strasburg’s line score.

“How he feels,” Menhart said, recalling his experience with Zimmermann. “I really don’t care how he does. That’s secondary. It’s all about he feels. I’m talking to him between innings, maintaining a nice dialogue, keeping him calm. He’s getting ready to pitch again for the first time where it matters. It’s the minor leagues, but it really does matter. You’re excited and anxious to see if you lost any stuff. All of that kind of plays a part in their head.”

What is inside Strasburg’s head as he nears the majors? Few people know for sure. The Nationals did not make Strasburg available for comment. Even Zimmermann, the person in the Nationals’ organization who best knows what Strasburg will be thinking and feeling Sunday afternoon, has not spoken to him.

“He hasn’t called me,” Zimmermann said. “So I figure I’ll just let him be.”