Stephen Strasburg casts a shadow on a bright day in Miami Gardens. (J Pat Carter/Associated Press)

Their season began seven months ago on a back field in Viera, Fla., when the Washington Nationals paired off and played catch. The partners formed parallel rows along a foul line, extending farther apart except for one player. His ongoing recovery from Tommy John surgery prevented Stephen Strasburg from tossing the ball more than 45 feet.

Their season ended Wednesday afternoon at Sun Life Stadium, where Strasburg at once announced his full return to dominance and offered a final glimpse of how the 2012 season could look with him at the top of the Nationals’ pitching staff. Strasburg struck out 10 in six scoreless, one-hit innings in the Nationals’ 3-1 victory over the Florida Marlins. Strasburg’s return had already been one of the most pleasant stories of this Nationals’ season. He provided an exclamation point Wednesday that left fans already longing for spring.

“He’s now one of the boys,” Manager Davey Johnson said. “He’s back. That was more than a teaser.”

This was supposed to be the season in between for the Nationals, the year they waited for Strasburg to heal and for Bryce Harper to develop. They made it something more. Never dull, the Nationals went 80-81, their best record since 2005, the year baseball returned to the District. While young players developed and Jordan Zimmermann and Strasburg each proved the fitness of their right elbows, the Nationals convinced the baseball world they might become contenders in 2012.

“We think we made great progress,” General Manager Mike Rizzo said. “We feel good about where we’re at. We still came in third place, which is not where we want to be. But we see progress. When we look back three years and we were a 59-win team, we feel pretty good.”

After Wednesday, any team with Strasburg headlining its rotation would look like a postseason candidate. Strasburg retired the final 13 batters he faced and struck out eight of those. At one point, Strasburg struck out eight in a span of nine hitters, reaching 99 miles per hour with his fastball. Only a flared single to shallow left field by Gaby Sanchez with two outs in the second inning prevented Strasburg from a chance at a no-hitter.

In five starts this season, Strasburg posted a 1.50 ERA in 24 innings, striking out 24 and walking only two. He has adopted a new approach of trying to induce weak contact, focusing more on precision than power. It didn’t quite work out to plan Wednesday afternoon, when he had his highest strikeout total since his unforgettable June 2010 debut. It was still something to behold.

“It was a big step in the rehab process,” Strasburg said. “I think right now, I’m pretty much done with the rehab. Now it’s healthy going into the offseason. I’ll be ready to go in spring training.”

Improved command allowed for more strikeouts. More important for Strasburg, he recaptured the ability to throw his curveball for strikes. Strasburg had been searching for the pitch all month. Wednesday, he threw 11 of 16 for a strike, including the strikeout pitch that buckled Marlins slugger Mike Stanton.

“I wasn’t going to be too hard on myself knowing that it’s only a pitch I had started throwing at the beginning of July,” Strasburg said. “It’s something that’s going to come back. It’s just reps and feel. Today, I had it back. I’m going to go into the offseason and know it’s going to be there in the offseason.”

The Marlins drew two walks in the second, too, the first free passes Strasburg had issued in the majors after the surgery. Back to last season, Strasburg had gone 117 batters without walking any of them.

He threw 79 pitches, and the Marlins swung and missed at 15 of them. He struck out seven of the eight Marlins position players, and he got strikeouts with all three of his pitches. Batters swung late at fastballs, whiffed at change-ups in the dirt and watched curves glide over the plate.

“He’s in preparation-for-spring training mode instead of rehabilitation mode,” Rizzo said.“Which is what we’re looking to do.”

Shortstop Ian Desmond gave Strasburg all the support he needed with a two-run single in the fifth inning. Ivan Rodriguez caught Strasburg and received an ovation from the final baseball crowd in Sun Life Stadium history, causing him to doff his cap. The Nationals’ bullpen sealed the game, fittingly concluding with Tyler Clippard’s 1-2-3 eighth inning and Drew Storen’s 43rd save. The Nationals finished their season with something that had become strangely common: a win.

If 2011 was not the year the Nationals charged into contention, it was at least the season they developed an aptitude for competence. They lost by more than four runs just 15 times all season, and they performed no major function at a level that merited embarrassment. They refused to play punch line.

Their offense came closest to causing them humiliation. The Nationals struck out 1,323 times, most in the majors and ninth-most all time. But they still scored more runs than six teams - near the bottom but not at the bottom. The Nationals’ starting rotation combined for an ERA less than 4.00, and the league hit .231 against their bullpen. They made 23 fewer errors this year than last. They had a fighting chance.

“This was truly the first year where our talent was enough that we had a real, legitimate chance to win every day,” third baseman Ryan Zimmerman said. “It’s definitely the best team we’ve had since I’ve been here.”

Even in good times, they did not relinquish their flair for the outrageous. On June 23, the Nationals concluded a thrilling homestand with a walk-off victory over the Seattle Mariners. They had won 11 of 12 games and surpassed .500 in June for the first time since 2005. As players finished their celebration, Jim Riggleman delivered on a threat he had made 45 minutes before the first pitch and resigned because of discontent with his contract situation. Shock replaced joy. Laynce Nix, who minutes earlier had hit the game-winning sacrifice fly, said, “I don’t even know what to think.”

“We had a bomb go off right in the middle of our clubhouse, right in the middle of our biggest win streak,” right fielder Jayson Werth said. “Start over. You guys are hot and rolling. The snowball has been built and it is rolling down the hill. Boom. Go back to the top. Start over.”

The Nationals culled Davey Johnson from the front office and installed him as their manager, a 68-year-old whose most recent managing experience came in the Florida Collegiate Summer League. The Nationals stumbled a bit as he bent the roster to his liking, but by September they started rolling again. The Nationals won 14 of their last 18 games and went 17-10 in September, third best in the National League.

September often lies. But the Nationals came away convinced that their performance this month foreshadowed greater things to come. Four pitchers 25 or younger populated their pitching staff for the final month. They swept the Phillies in Philadelphia. They took two of three from an Atlanta Braves team fighting for its playoff life.

Through every moment, the Nationals liked each other. They wore Beast Mode T-shirts. In the outfield every afternoon, the pitching staff split into teams and played Ultimate Frisbee. Following home runs, players dropped flying elbows on each others’ helmets. In the clubhouse after games, veterans gathered around a television, watched West Coast games and drank cold beer.

“It’s September and we’re not in contention, we could just sit here and feel sorry for ourselves,” Storen said. “We’re having a blast, day-in and day-out. We have fun.”

The manner in which they ended their season, with Strasburg leading the way, suggested there will be more fun ahead.