Nationals Manager Davey Johnson informed Stephen Strasburg this morning he will not pitch again this season, ending the ace’s season after 159 1/3 innings with 24 games remaining and the Nationals leading the National League East by 6 1/2 games, Washington’s first postseason since 1933 within their grasp.

Johnson believed Strasburg had become distracted by the immense media coverage of the innings limit the Nationals imposed as he pitches his first full season following Tommy John surgery. The Nationals had planned to let Strasburg make one more start on Wednesday in New York. But after Strasburg allowed the Miami Marlins five runs in three innings Friday night, the Nationals decided to end his season now instead.

“The media hype on this things has been unbelievable,” Johnson said. “I feel it’s as hard for him as it would be anybody to get mentally, totally committed in the ballgame. And he’s reached his innings limit. So we can get past this and talk about other things for a change.”

Johnson consulted with General Manager Mike Rizzo and pitching coach Steve McCatty late Friday night. They all believed Strasburg had lost focused because of the impending shutdown. Rizzo planned before spring training began he limit Strasburg’s innings to roughly 160. The question was precisely when, and his performance last night convinced the Nationals the time is now.

“After yesterday’s start, we just figured that mentally and physically, Stephen looked like he was fatigued,” Rizzo said. “We decided, what’s the difference of 1 59 1/3 innings or 163 or 164 or 165 1/3 innings? We said let’s pull the plug today and move on with the season and try and finish the season off positive.

“When you put two and two together with the parameters we had in place already, it was a fairly easy decision to say, let’s pull the plug after today instead of having one more start and six more innings.”

At around 10:45 this morning, Johnson sidled next to Strasburg in the Nationals’ training room. “I wasn’t going to drag it out,” Johnson said. “I’m just taking the ball out of his hands.” Johnson said Strasburg was “emotional” about the decision.

“I know he’s been struggling with it for weeks,” Johnson said. “I know he doesn’t sleep good thinking about it. Shoot, I’ve heard so much advice from every ex-pitcher, every guru on the matter.”

“If you’re not there 100 percent mentally — I mean, he’s a gifted athlete. His velocity could still be there,” Johnson added. “I don’t see the crispness. I don’t see the ball jumping out of his hand. It’s more, I’m a firm believer this game is 90-95 percent mental. He’s only human. I don’t know how anybody can be totally concentrating on the job at hand and media hype to this thing. I think we would be risking more sending him back out.”

Strasburg’s season ends with his ERA at 3.16, which is fourth in the Nationals’ rotation. He struck out 197 batters, second in the National League, and walked only 48.

“It would have been nice for it end on a positive note,” Rizzo said. “But he’s had a terrific season. You couldn’t ask for anything more coming off his first season on Tommy John surgery. He got us to where we’re at right now. He’s a huge part of where we’re at right. He’s one of the major contributors to the first-place ball club.

“We’ve got a lot of bright and happy days ahead of us watching Stephen Strasburg pitch. This is something that he’s going to have to accept that it’s on his best behalf, and we’re going to move on from here.”

Rizzo made the decision to limit Strasburg’s innings last year, as he made his first starts following his September 2010 ligament-replacement surgery. Strasburg pitched only 44 innings last season, between the major leagues and minor leagues, which played into the decision as much, if not more than, the elbow reconstruction surgery.

Rizzo made the same decision last season with Jordan Zimmermann, who stopped pitching after 161 1/3 innings. In planning Strasburg’s workload, Rizzo found young pitchers who face a large increase in innings become far more prone to serious injury. Rizzo keeps the summary of the Nationals’ research in a stack of loose-leaf papers that measures 1 ½ inches thick.

“Business as usual,” Rizzo said. “It was a plan that we put in place back on Feb. 1. We’ve been true to the plan the whole way, and we haven’t wavered from it one bit. This is just a culmination of that plan. I think I believe in my heart that it’s the right thing to do for the player. The right thing to do for the player is the right thing to do for the franchise.”

In his final three starts, Strasburg demonstrated the effect coming back from Tommy John surgery has on many pitchers. The Marlins drilled him for seven runs in five innings, including a career-high nine hits, on Aug. 28. Last Sunday, he shutout the Cardinals for six two-hit innings. And then last night, partly because of his lack of focus, Strasburg got drilled again.

“That’s typical of Tommy John rehab patients,” Johnson said. “Often times, it’s not the velocity or the arm strength that’s the first sign of fatigue. It’s the delivery. Is he online, or is he falling off? Can he finish his pitches? Is there hop on the fastball even though it’s 95, 97 miles an hour? Is he finishing off his breaking pitches, his changeup, which is a very important pitch for him that’s a very stressful pitch on his arm?

“You take all those things into consideration, and it very much resembled Jordan’s season last year. Maybe a little less up-and-down than Jordan had.”

Left-hander John Lannan, a two-time opening starter for the Nationals who spent all year in Class AAA, will take Strasburg’s spot in the rotation. Even without Strasburg, the Nationals have four starters who rank in the top 18 in the National League in ERA and three in the top 10. If you remove Strasburg, the Nationals’ rotation has a 3.31 ERA – still the best in the major leagues.

“I love my rotation,” Johnson said. “Very talented. And Lannan is plus also. He’s 2-0. So I feel good about where we’re at.”

Strasburg has kept any expansive thoughts on the matter private. He told reporters he would to fight with his team “to the end” and that he remained focused on his next start. Teammates and those close to him say he desperately wants to keep pitching, that he is willing to gamble his future in a way the Nationals are not.

“Stephen wants to pitch,” said Scott Boras, Strasburg’s agent, who has publicly backed the Nationals’ decision. “When you’re a competitive athlete, you want to perform. On the other side of it is, the doctor saved his career. He’s very beholden to the doctor. When you’re smart like Stephen Strasburg is, your competitive desire in the whole thing has to pay credence to medical science.”

Even though he will not pitch, Strasburg will remain with the Nationals. He has not been removed from the roster. He will spend each game watching from the dugout, wishing the Nationals were as willing to gamble on his future as he is.

Strasburg is “a part of this team,” Johnson said. “He wants to be helping until the end. He doesn’t want to let the team down. That’s the emotional part, the professional part on his side. He’s willing to risk it being his last year to have that. I understand that. But it’s our job to make sure it’s not another Mark Prior or anything like that.”