SAN FRANCISCO -- Michael Crabtree stepped back into the lineup, and suddenly the 49ers went from high offensive anxiety to footloose improvisation.
From stalled and steamed to a wave of production and rolling laughter, just like that.
Ladies and gentlemen, for your entertainment pleasure ... the San Francisco 49ers offense (which doesn't stink anymore)!
"It's always good to have these two at your disposal on the field to make plays," Colin Kaepernick said in a relaxed postgame podium appearance with Crabtree and Anquan Boldin.
Of course, the 49ers' 23-13 victory over St. Louis on Sunday was about more than their top receiver's 2013 debut after an offseason Achilles injury and the instant camaraderie in evidence.
There was -- as always -- the 49ers' stout defense, an offensive line holding up despite a run of injuries, Vernon Davis' two amazing hurdle leaps, and very solid special teams play.
All right in time for the rematch against Seattle back here Sunday, which the 49ers must win to have any hope of winning the NFC West.
But to get to the heart of the 49ers' emotional rescue, you had to see Crabtree, Boldin and Kaepernick laughing and teasing each other Sunday.
Mostly, you had to listen.
Michael, why were you grimacing after your 60-yard reception in the third quarter down to the Rams' 20-yard line?
"I'm supposed to take that to the house!" Crabtree said, shaking his head as his buddies giggled about his double move past the corner but his slide to the ground after other defenders tracked him down.
Colin, your thoughts?
"Yeah, man," Kaepernick said after a dramatic pause, "he's supposed to score!"
This was only about 50 times more lighthearted than any 49ers public utterance in several months, and it was perhaps Kaepernick's loosest display as an NFL entity.
Then Boldin added: "We give (Crabtree) a pass on that one. Thanksgiving was this week, so ..."
More Crabtree: "You're the one serving me all the turkey!"
Now, I should point out that the 49ers offense largely broke out of its midseason slump with a decent effort last Monday night in a victory in Washington.
But Sunday was the return of Crabtree -- someone who caught 85 passes for over 1,100 yards last season -- it was at home, and it was right before the Seattle game.
So the 49ers were naturally brimming with expectations heading into this game as Crabtree jumped right back into the starting lineup alongside Boldin.
Crabtree delivered by playing 38 of the 49ers' 62 offensive snaps, catching one short pass in the first half and then that 60-yard gainer in the third quarter, which tied Crabtree's career-long gainer.
And, oh, he also was flagged for a block in the back and offensive pass interference on the 49ers' opening possession.
"Had to get those jitters out," Crabtree said, shaking his head. "Hadn't played in a long time -- I was just all over the place today.
"But like I said, I'm just happy to be out there. I had fun today."
And what was it like for Boldin -- acquired last offseason from Baltimore -- to play with Crabtree for the first time?
"You know, it's about time he gets double-teamed now," said Boldin, who proved it by catching nine passes for 98 yards Sunday.
"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. Good to have him back."
Before this game, the 49ers hadn't had two wide receivers both total more than 45 yards in a single game this season.
And they've had five games when the No. 2 receiver gained fewer than 10 yards, including two when only one receiver gained any yards.
So presuming Crabtree will get only stronger as this season goes on and into the postseason, this is dramatic stuff for the 49ers offense.
"He's always been a big-time game player," coach Jim Harbaugh said. "If there is a thing, he is that.
"You anticipate that."
Crabtree said he wasn't quite at 100 percent Sunday, but he said he was "at game speed," and that he was more than ready to contribute to the playoff run.
The important thing is that Crabtree is back, and now everything is looser and louder around the 49ers, and for now -- just in time for the Seahawks -- the dark cloud is gone.