SANTA CLARA, Calif -- Colin Kaepernick likes to tweet that he does not get tired. Fair enough.

But surely, after committing four turnovers in the San Francisco 49ers' 28-20 loss to the Chicago Bears in the Levi's Stadium regular-season debut, the 49ers quarterback had to be weary of giving the ball back to the visitors.

Colin Kaepernick kept the Bears off balance early, but his miscues evaporated the 49ers' advantage. AP Photo/Tony Avelar

"Terrible," was how he described his performance in the 49ers'meltdown in which they led 20-7 entering the fourth quarter and 17-0 late in the second quarter.

Kaepernick completed 21 of 34 passes for 248 yards and a touchdown. But he was picked off three times, was sacked four, lost a fumble and had a passer rating of 57.0, the third lowest of his 25 career starts.

Plus, he had an unsportsmanlike conduct penalty for "inappropriate language" late in the collapse.

"I didn't say anything," Kaepernick said.

Asked if he was shocked at the description of the penalty, Kaepernick said he was. Niners coach Jim Harbaugh said he was not given an exact reason for the penalty, which came after Kaepernick's second interception and preceded by one play the Bears' taking a 21-20 lead.

"It stings to lose," Harbaugh said. "We all have our fingerprints on it."

Kaepernick's more than any one else, though, if for no other reason than his hands were on the ball for every Niners snap. Such is life for a quarterback.

And yet, the game started well for the dual-threat QB. The read-option was again in vogue, and Kaepernick was keeping the Bears off balance early and often.

In fact, his 66 yards rushing were more than the Bears had as a team (46), though, to be fair, Jay Cutler led Chicago's feeble rushing attack with 25 yards.

But it was on a run up the middle in the second quarter, one series after Bears safety Chris Conte made an acrobatic, outstretched interception 19 yards downfield, where Kaepernick's ball security skills as a runner failed him.

After picking up 4 yards, Kaepernick lost possession when Jared Allen stuck his helmet on the ball, popping it out for safety Danny McCray to jump on for the recovery. The 49ers led 10-0 at the time, though.

Kaepernick's final two interceptions came in the fourth quarter, both by rookie cornerback Kyle Fuller, and both picks were followed by Bears touchdowns.

Ballgame.

"I was using my technique and just doing my job," said Fuller, whose role increased when starter Charles Tillman went down with a triceps injury. "I was just in the right place at the right time."

Or, as many would note, Kaepernick again fell into that trap of going for the home run ball and staring down his receiver, while his checkdown options were wide open underneath or in the flat.

"As far as my decisions, I saw the coverages, I went where I wanted to with the ball," Kaepernick said. "I just didn't make the plays and I didn't make the throws."