EARTH CITY, Mo. -- It is NFL custom for successful running backs to take care of the offensive linemen, tight ends and fullbacks who open holes for them during the course of the season.

But what happens if the two backs you have created so much space for are both rookies? Taking it further, what if one is a fifth-round pick and the other an undrafted free agent?

Such is the position of Rams tight end/fullback Cory Harkey.

“We haven’t been out to eat yet but we’ve been talking about it,” Harkey said, laughing. “We don’t get on them that much about it.”

If the Rams running game continues rolling like it has, maybe it’d be best if Zac Stacy and Benny Cunningham came up with a creative way to say thank you, with Harkey at the top of the gift-giving list.

Perhaps lost in the mix of the Rams’ revamped rushing attack is the revelation that Harkey has been since he began playing much more. Sure, the Rams installed Stacy as the starter after the Week 4 debacle against San Francisco but Harkey also became a far more integral cog in the attack in the immediate aftermath of that game as well.

Through the first four weeks, Harkey played a grand total of 11 snaps, mostly at tight end while the Rams pursued packages with more receivers and fewer tight ends.

After coach Jeff Fisher decided his offense needed a new direction, one in which the running game would become more of a focal point, he also decided that one of the directions to take would be directly behind the 6-foot-4, 260-pound Harkey.

Of course, for that to happen, Harkey would have to become more versatile than his usual role as an inline blocker at tight end. Fisher and tight ends coach Rob Boras had Harkey doing some experimental work at fullback during the spring and summer as Lance Kendricks missed time with an injury.

Harkey’s task became turning those practice repetitions at fullback into game-time production, something he hadn’t done since his first two years at UCLA. He turned to fellow tight ends such as Kendricks and Mike McNeill, players who have experience doing a little bit of everything, for advice on how to become a more well-rounded player.

“Coach talked to me before all this happened about me doing some stuff out of the backfield but I want the team to be good, I want to be good, I want to be successful,” Harkey said. “So I knew I was going to do whatever I can to help this team win. This has been that role for me.”

That role has continued to expand every week, as Harkey grows more and more comfortable in his new surroundings. He played 38 snaps against Jacksonville just a week after the Rams decided to rev up the running game. In the seven games since that San Francisco loss, Harkey has averaged almost 31 snaps per game.

Harkey has still done some work attached to the line of scrimmage as a tight end but he can regularly be seen leading Stacy or Cunningham through the hole and instigating head-on collisions with linebackers and defensive backs. He’s even chipped in six catches for 53 yards and a touchdown though he’s also responsible for three drops.

Adjusting to moving in space and covering up defenders remains a work in progress but evidence of Harkey’s growth was on display last week against Chicago.

Witness Harkey’s big block on Chicago linebacker James Anderson to clear Stacy for an 11-yard gain on the first play from scrimmage. Or Harkey taking on and locking up Bears end Shea McClellin on the edge to lead Stacy for a 35-yard run.

“For me it’s just that and you have got to stay low every play, get a good push on guys,” Harkey said. “You are going against guys who are a little bit more athletic and also strong and big so just having good leverage, good knee bend and being able to bring some pop.

“I’m getting used to it. I think it’s been a good place for me. I am still trying to do everything, in-line blocking and everything. I think they like what I can do back there so it’s been good.”

Indeed the Rams are quite pleased with what Harkey is bringing to the table both in terms of production and intangibles.

“Cory’s done a great job,” Fisher said. “He stepped up when Lance was down. He’s doing a lot of different things. He’s lining up at the tight end position. He’s our move guy at fullback, and he’s really got a good sense for that and feel for that as far as attacking linebackers and DBs.”

Much like his thankless position on the field, Harkey also doesn’t get much credit for what he brings to the huddle and locker room, either. The soft-spoken Harkey is always polite and humble in interviews but never strikes you as a fiery leader type.

Quarterback Kellen Clemens said Harkey is actually a bit of a sparkplug for the offense.

“I love Cory Harkey,” Clemens said. “I absolutely do. He’s very versatile. He’s very smart. He’s a very hard worker. You love to play with guys like Cory Harkey. The other thing that he does that I think goes unnoticed sometimes is he brings a lot of energy. He’s kind of a pump-up guy sometimes. He has a very, very unique role on this football team and he fills it and we’re very glad to have him.”

In some ways, Harkey fills a unique but evolving role in the NFL at large. True fullbacks have been headed toward extinction for some time but more and more teams are looking for tight ends with the versatility to do both. Kendricks did a lot of it last year and he still does but Harkey has joined him in their many movements.

Although it’s taken some getting used to and Harkey is still a ways from having mastered the position, he’s got the first requirement of playing fullback down, for he really enjoys high speed collisions.

“It’s pretty fun,” Harkey said. “I like it. I think some of the tight ends will agree that I kind of like that action so it’s good.”