SAN FRANCISCO -- What's wrong with Colin Kaepernick?

It has been a common theme this year in media and fan circles.

After seeing him with a full complement of offensive weapons Sunday for the first time this season, that line of questioning may dissipate.

Kaepernick looked calm, cool, confident and efficient in the San Francisco 49ers' 23-13 victory over St. Louis Rams on Sunday as San Francisco sent the rest of the NFC an early-December message: A healthy 49ers' offense is a dangerous offense.

It's no coincidence Kaepernick looked far from being a detriment Sunday. Star receiver Michael Crabtree made his 2013 season debut after being out with a torn Achilles he suffered in May. For the first time since the Super Bowl, Kaepernick had a full cache of weapons. It was also the first time the team's top three receivers -- Crabtree, tight end Vernon Davis and Anquan Boldin -- played together.

If this group (as well as fourth option Mario Manningham, who played little Sunday because the 49ers used a lot of double tight-end sets) can stay healthy, it will be extremely dangerous down the stretch for the 49ers, who are 8-4 and in control of the sixth and final NFC playoff seed heading into the final quarter of the season.

And it will probably make Kaepernick, in his first full season as the starting quarterback, look as good as he did during last year's Super Bowl run.

"Colin was dynamic," San Francisco offensive lineman Adam Snyder said after the game. "He's been good all year, but give him these weapons and he is going to get a lot done."

He did Sunday, going 19-of-28 for 275 yards. There's no doubt, Kaepernick is more comfortable with a full complement of receivers.

In Week 4 against St. Louis (playing without Crabtree and Manningham), Kaepernick went 8-of-15 for 96 yards against the Rams' standard four-man rush. According to ESPN Stats & Information, against the same pressure Sunday, Kaepernick was 15-of-20 for 233 yards and a touchdown pass.

When facing a non-blitzing situation during the first 11 games of the season, Kaepernick completed 57.9 percent of his passes, averaged 7.2 yards per attempt and threw six interceptions. Against a four-man rush Sunday, he completed 75 percent of his passes, averaged 11.7 yards per attempt and was not intercepted.

Kaepernick's success against the Rams' standard pass rush, considered one of the best in the league, will likely force opposing defensive coordinators to consider different approaches and perhaps decide to blitz more often. That could create more opportunities for this offense.

That's the beauty of Crabtree's return for Kaepernick and the 49ers' offense. He opens up schematic advantages and secondary reads for the 49ers that simply were not there earlier in the season and made Kaepernick's job more difficult.

With Crabtree back (he had two catches for 68 yards), the pressure instantly came off Boldin and Davis. Boldin had one of his best games with the 49ers, with nine catches for 98 yards, and he may be the key to this offense in the final weeks. He will no longer get the brunt of the defensive coverage, as he excels as a second or third option. He showed that Sunday.

"It's about time he gets double-teamed now," Boldin joked, speaking of Crabtree. "When you have a guy like that on the other side, it definitely relieves pressure off of you. It frees you up to just go out and play ball. It's good to have him back."

Last season, Crabtree was targeted on 34 percent of the 49ers' offensive plays. It was the second highest rate in the league. That opened up opportunities for Davis, a star in the final six games of last season. Those chances opened up Sunday as well. Davis had four catches for 82 yards and a touchdown.

Inside the 49ers' walls, the team has supported Kaepernick, feeling good about his play and his field maturation amidst the challenges. Now, after seeing Crabtree's impact on the offense and how he can help Kaepernick, there is serious excitement.

"We can only get better," San Francisco fullback Bruce Miller said. "Colin's been great all season and having all of the guys back are just going to make him better."