SAN JOSE, CA - NOVEMBER 25: Tomas Hertl #48 of the San Jose Sharks skates against the Chicago Blackhawks at SAP Center on November 25, 2015 in San Jose, California. (Photo by Rocky W. Widner/NHL/Getty Images)

EL SEGUNDO, Calif. – For Tomas Hertl, success in the NHL came almost too quickly.

As a 19-year-old rookie in 2013-14 he was known as the player who could roof a goal shot through his legs. The San Jose Sharks fans fondly called him “Teenage Mutant Ninja Hertl.” He had size, mobility, strength, and a youthfully charming look in his face.

At the age of 22, Hertl still has the same attributes, but gone is the promise of hope that he would be San Jose’s next superstar, taking over for Joe Thornton and Patrick Marleau.

He has potential, but there’s enough of a body of work since his rookie year, when he scored 15 goals and had 25 points in 37 games before a knee injury, to see that maybe the success raised expectations too high.

“I think with a lot of young players they’re capable of coming in for 10, 20, 30, 40 games, but this is a man’s league and to do it over 80 games and do it consistently year after year, you have to learn that,” Sharks coach Peter DeBoer said. “I don’t think he’s any different than any young players in that. He’s not the first young guy to come in and have some short-term success but it’s about building a career and I think that’s where he’s at now.”

Only four games into his NHL career, Hertl – the 17th overall pick in the 2012 NHL Draft – made a name for himself. He scored four goals against the New York Rangers and looked like a star in the making. He continued his torrid pace with 21 points and 13 goals in the season’s first 26 games. But then he was hit by Los Angeles Kings captain Dustin Brown in a knee-on-knee collision on Dec. 19, and was out until early April after knee surgery.

“I think coming back from a knee injury too, I’ve never experienced it myself, but it’s hard adjusting to the speed of the game again and getting confidence with that knee,” Sharks forward Joe Thornton said.

Hertl notched five points in San Jose’s seven-game playoff loss to the Kings in the postseason, but in the subsequent years, he hasn’t regained the form from early in his rookie year. A year ago he scored just 13 goals and notched 31 points in 82 games played. This year he’s on pace for seven goals and 32 points. So far, Hertl has three goals in 33 games.

This was supposed to be a bounce-back year for the young Czech. He changed his diet, going mostly gluten free after a blood test, and leaned up so he could have more energy during games. He claims he feels better, but the results have still been tough to find.

“Sometimes I’ll (eat) gluten free, sometimes not, and up and down. The summer time was very easy. I have everything at home. I’m trying, and we’ll see. I like it, food … I eat gluten free if I have the chance,” Hertl said. “I think so I have a little bit more energy.”

This has also been Hertl’s first season at center full-time. He was supposed to provide some scoring depth on the lower lines, but with the oft-injured Logan Couture having played in just five games this season, Hertl’s played a larger role, which has forced him to speed up his learning curve.

“(His rookie year) was such a little glimpse but you saw what he’s capable of and I think it’s such a high ceiling for him, he’s going to continue to get better and better,” Thornton said. “He’s playing center now and I think that’s probably a better position for him, but I think he’s going to be a real good player for us.”

Few center have his size and speed and offensive nature. The problem just may be his inability to finish. He held a 15.3 percent shooting percentage as a rookie. This year he’s down to 3.7 percent.

According to War-on-Ice, Hertl's Corsi-for percentage 5-on-5 is at 53.62 percent. His Corsi-for percentage relative 5-on-5 is plus-5.52 percent. Both are positive markers of puck possession.

“The first season was amazing for me and I for sure need a little bit more goals,” Hertl said. “I have lots of chances and lots of ice time and I just keep shooting and keep around the puck and working hard and hopefully they’ll come soon.”

Plus, he’s still just 22 years old, which is tough to remember considering how much success he had two seasons ago. In all likelihood, he hasn't reached his ceiling as a player

“I think he’s taken some pretty good strides this year as far as his battle and compete level,” Marleau said. “He has a tremendous upside to him.”

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Josh Cooper is an editor for Puck Daddy on Yahoo Sports. Have a tip? Email him at puckdaddyblog@yahoo.com or follow him on Twitter! Follow @joshuacooper