NEW ORLEANS (AP) — Under pressure and off balance, Colin Kaepernick released a fourth-down throw into the end zone with the outcome of the Super Bowl hanging in the balance.

Everyone in the Superdome could see that the ball wasn't caught as it sailed over Michael Crabtree. Enraged San Francisco coach Jim Harbaugh argued for why: He thought Crabtree got held, bumped by cornerback Jimmy Smith with safety Ed Reed trailing the play.

"There's no question in my mind that there was a pass interference and then a hold on Crabtree on the last one," Harbaugh said.

The San Francisco 49ers' remarkable unbeaten run in their first five Super Bowls ended with a 34-31 loss to the Baltimore Ravens on Sunday night, though they nearly pulled off the greatest championship comeback yet.

With three chances from the 5 and less than 2 minutes remaining, Kaepernick threw three straight incomplete passes intended for Crabtree, including the last on which Harbaugh screamed from the sideline and signaled for a penalty.

Kaepernick hardly reacted, lowering his head slightly and walking slowly off the field.

"That wasn't the original option," Kaepernick said. "It's something I audibled to at the line based on the look they gave us."

No comeback this time in the Big Easy.

Kaepernick got tripped up and tossed down, then nearly rallied his team once more in his 10th career NFL start.

Still, with Kaepernick leading the way, the 49ers thought they had it.

"I think everybody was thinking that," right guard Alex Boone said. "Execution in the red zone wasn't where it was supposed to be today. It's a bad feeling."

Rarely rattled on an impressive path to the Super Bowl, Kaepernick — San Francisco's gutsy second-year quarterback with those speedy legs — finally showed some inexperience on football's big stage. Not to mention some guts.

After a remarkable postseason run by the tattooed play-caller, the Ravens exposed plenty of flaws in handing Kaepernick and Co. despite San Francisco's second-half rally.

"We were ready for the second half," Kaepernick said. "We knew we had to score to get back in the game. We had good plays, we had bad plays in the red zone."

No team has come from more than 10 points down to win a Super Bowl, and Kaepernick had a chance to make it happen less than three months after becoming San Francisco's starter.

He regrouped during a 34-minute delay early in the third quarter because of a power outage, finding his groove and turning the Super Bowl into a wild game down the stretch — and gave yet more credibility to the pistol offense designed by his old college coach that is so well suited for the NFL's young, mobile quarterbacks.

"Colin was cool the entire game," left tackle Joe Staley said. "Colin was the same he's been the whole entire season. He's never shown any hints of being rattled, any hint of being uncomfortable on the football field, and he showed that exact kind of character today."

Kaepernick directed four second-half scoring drives, throwing a 31-yard touchdown pass to Crabtree and also running 15 yards for a TD. But the 49ers missed the two-point conversion that would have tied the game with less than 10 minutes left.

Crabtree didn't get much help in a mistake-filled first half by San Francisco (13-5-1), which failed to stop Joe Flacco and deliver the franchise's sixth championship that would have matched the Pittsburgh Steelers for most ever.

The 49ers' perfect Super Bowl record? That's over, too. They lost for the first time in the title game. Continued...