Last season, Bryce Harper hit .274 with 20 home runs and 58 RBIs, but he played in just 118 games.
(John McDonnell/The Washington Post)

Bryce Harper is already experienced and talented enough to be looked at as one of the leaders inside the Nationals’ clubhouse.

At the same time, the 21-year-old’s fiery personality and occasional outbursts make it easy to remember just how young he still is as he enters his third big league season.

On Wednesday, Harper got ejected from a spring training game. The outfielder had to be separated from first base umpire Jeff Gosney in Washington’s 3-2 loss to St. Louis. After Gosney called him out on a close play, Harper uttered something that resulted in him being thrown out.

“You must play the game with emotion,” Nationals first-year manager Matt Williams told The Washington Post after the game. “Bryce wants to be safe there. My thought is, he could express it in a better way and not necessarily get thrown out of the game. But he must play with emotion. We’ll certainly have many talks about situations like that and go forward.”

While he may still show some immaturity, Harper’s dedication off the field and production on it is something his teammates can count on.

The first overall pick in the 2010 draft, Harper was named NL rookie of the year in 2012 and has made two consecutive All-Star Game appearances.

He arrived to spring training in excellent condition, aided by a diet filled with whole foods and organic produce.

Partly due to Harper, the Nationals — who open the 2014 season Monday in New York against the Mets — are once again a trendy preseason pick to contend for a championship. For the second consecutive year, Sports Illustrated is predicting the Nationals to win the World Series.

A healthy season from Harper would help reach those lofty expectations. He has a ferocious approach to the game and has suffered quite a few injuries as a result. After crashing into two outfield walls a year ago, he sustained knee bursitis — which bothered him all season. Harper hit .274 with 20 home runs and 58 RBIs, but he played in just 118 games in 2013.

After offseason knee surgery, Harper lifted weights to add muscle to his frame and trimmed down to 220 pounds before spring training. Harper has stated he’s healthy and won’t be risking any further structural damage to his knee.

But Harper’s offseason work and overall approach to the game hasn’t impressed his peers, who voted him the most overrated baseball player in the league in a recent poll conducted by ESPN The Magazine.

Harper seems primed for the challenge to proves his critics wrong.

“Once those lights come on, it’s a totally different ballgame,” Harper told The Washington Post on Monday. “Everybody knows that. I’m excited for day one. I’m excited to get going. We’ll see where I’m at March 31.”