Greg Robinson back home at left tackle

EARTH CITY, Mo. -- As Greg Robinson attempted to adjust to playing left guard for the first time during the preseason, he often found himself bouncing back and forth between his new position and his old one.

Robinson was less than a year removed from playing left tackle, the only position he's ever really known, for SEC champion Auburn. Robinson was so dominant on the edge that the St. Louis Rams made him the No. 2 overall pick. With Jake Long already entrenched at left tackle, the Rams had long-term plans for Robinson to eventually take over at left tackle while contributing right away at guard.

When Long suffered the second season-ending ACL injury of his career last week against Kansas City, the future accelerated into the present. After just three starts at left guard, Robinson is back home.

"In some ways it is natural," Robinson said. "I just feel more comfortable out there. It’s going to be a learning process, also, but I don’t think it’s going to take me as much time as it took me to get used to guard."

In theory, Robinson is correct. Left tackle is his normal position, the one he knows best. And it took him a while to get used to playing in tight space at guard while also taking reps at tackle. Robinson didn't make his first start until the team's fifth game, the first meeting against San Francisco.

Now that Robinson is moving back outside, he should be able to adjust quickly to playing in space and having less to worry about in terms of communication and combination blocks with the center and tackle.

That doesn't mean that Robinson won't have his share of bumps along the way, though. Of the 178 snaps Robinson has played this season, only 21 of them came at left tackle, all coming last week against the Chiefs.

For the most part, Robinson held up OK but he also had his share of mistakes. His most impressive moment came when he ran down Chiefs safety Ron Parker to make a tackle after an interception.

"He had some issues, they had outstanding rushers, but he was strong and stout," Rams coach Jeff Fisher said. "That’s what he does. He’ll have a week to work on the footwork and things like that this week. He went out there and knew what to do and came out of the stack on a screen and executed a block. You can see his athletic ability when he made the tackle on the interception. At the tackle position, he’ll be fine.”

Big-picture: The Rams hope that Robinson will be more than just fine, but it's no secret that it will take him some time to nail down the nuances of pass-blocking at the NFL level. By Robinson's own admission, pass-rushers are faster and more athletic in the NFL, and Robinson comes from a system at Auburn that didn't ask him to do much pass-blocking.

After learning of Long's injury, Robinson said he and offensive line coach Paul Boudreau devised a list of what he needed to nail down and work on this week in practice. At the top of that list were notes on footwork and understanding angles. His trademark aggressive approach to run-blocking is one of his greatest assets, but it's also something Robinson knows he must monitor so he doesn't get out of control.

"I have just got to have good sets every time I go out there to block somebody," Robinson said. "And don’t be too aggressive and try to get my hands on guys as much as possible."

Sooner or later, Robinson was going to become the Rams' left tackle regardless of Long's status. Clearly, all parties would have preferred that it didn't happen as quickly or in the way that it did, but this is where the Rams currently stand.

For what it's worth, fellow tackle Joe Barksdale believes Robinson is up to the task.

"As a rookie, the hardest thing is coming in and learning the offense," Barksdale said. "You’ve been in the same offense for a number of years, same coaches and all of that. Then you come in and everything is new. The terminology, the people, from the feet up, everything is new to you. I think he’s done a really, really good job of overcoming that kind of shock and pretty much having to start your freshman year all over again. I think he’s coming along really well."

Robinson was drafted to be the Rams' left tackle of the future. That future is now.