By Jim Thomas

As he left Rams Park on Monday afternoon, Steven Jackson chalked up his angry sideline outburst Sunday to the heat of battle and the frustration of a wrenching 17-16 defeat to San Francisco.

"I was upset mainly because I thought we were going to come out on top," Jackson said. "I really thought we were going to win, and I was hoping that we could put together a successful drive and it just wasn't going that way. It was more a vocal out-letting of frustration than anything."

Jackson was seen yelling at coach Scott Linehan on the sideline after a third-and-7 pass from Marc Bulger to Drew Bennett fell incomplete on the Rams' second-to-last offensive possession of the game. Jackson had to be pulled away by running backs coach Wayne Moses. Jackson was blocking on the play.

There were a few plays in the game in which Jackson was open on pass routes, but the ball went elsewhere. He said not getting ball as a receiver had nothing to do with his anger.

"Oh, no, no, no," Jackson said. "I like to catch the ball a lot, but I understand it's not my (primary) job. I expect Marc to look for Isaac (Bruce) and Torry (Holt) before he looks for me. Always."

Bulger said he went with his first option a lot Sunday because of all the hits he absorbed. He simply didn't think he had time to scan the field for second and third option. Jackson said there are no pass patterns in the playbook where he's the No. 1 option.

"I'm never the primary," Jackson said. "I'm two or three the second or third option."

When quizzed Monday about Jackson's blowup, Linehan said it might have been over a pass-protection miscue.

"I'm not sure exactly," Linehan said. "Being that time of the game, there was probably something happening on protection on that down."

On the play in question, left tackle Alex Barron was beaten to the inside by a ***** pass rusher. Bulger was hit as he released the ball, and the pass fell short of Bennett.

Linehan played down the notion Jackson was upset specifically with him.

"I don't know if he was yelling at me," Linehan said. "I didn't take it that way. I honestly didn't. This is news to me. Sometimes players get emotional. I understand that part. You've just got to let it roll off your back. I don't have any issue at all with Steven. Sometimes he gets a little animated because he's a competitor. He didn't say anything to me that I heard."

Jackson had only 60 yards rushing against San Francisco. For the season, he has 118 yards rushing, and is averaging only 3 yards a carry. Entering the Monday night game, the Rams ranked 28th in rushing offense in the NFL.

"As we finished the season last year, expectations were high," offensive coordinator Greg Olson said. "We felt very good about where our run game was, and felt like we were going to be able take off this year where we left off a season ago. That's been a frustrating thing for us."

Jackson and the running game actually started strongly against Carolina and San Francisco, but slowed to a trickle as the games progressed. Early in the second quarter against the Panthers Jackson had eight carries for 44 yards, but he had 10 carries for 14 yards thereafter. Early in the second quarter against the ***** he had seven carries for 37 yards, but only 23 yards on 14 carries the rest of the way.

Matters aren't helped by the fact that the Rams' offensive line is minus right guard Richie Incognito and left tackle Orlando Pace because of injuries. Against San Francisco, Milford Brown was starting at right tackle for the first time as an NFL player; right guard Claude Terrell was starting his first regular-season game since 2005; and Barron was starting for the first time at left tackle in the NFL.

"The chemistry's not there," Jackson said. "Those five guys up front never played a whole game together. So hopefully, as we get into the season, and get into game shape, we can continue our dominance that we've had (early) and carry it over to the second half."