Safety Reggie Nelson did it again Sunday with his NFL-leading eighth pick and sixth off Ben Roethlisberger.

And suddenly, the Bengals' best season in the 16-game era went from a coronation to a wake in a matter of seconds Sunday with quarterback Andy Dalton maybe out for the rest of the year pending Monday's examination by a hand specialist.

At this point there's nothing solid until Dalton meets with the doctor.

After the 33-20 loss to the Steelers at sold-out Paul Brown Stadium, head coach Marvin Lewis ruled him out for next Sunday's game in San Francisco. But with Dalton confirming a fractured throwing thumb it looks like a daunting timetable that may be in the four-to-six-week range and could spell the end of the best season of his career.

"I'll know more tomorrow," said Dalton, who broke his throwing thumb making the tackle on defensive lineman Stephon Tuitt at the Steelers 7 after he intercepted Dalton's shovel pass on the Bengals' first drive with five minutes left in the first quarter.

"When I got to the sidelines, I tried to grip the ball. I felt like it was a little bruise that I could try and get through. Then I went and got the X-Ray," said Dalton, who has never missed a start in his career. "Mentally I'm fine. It's unfortunate it happened at this point in the season. But I'll do everything I can to get back as quickly as I can to help the team. I'm doing all right. There are people way worse off than I am."

The injury cut down Dalton with a career- and franchise-best 106.2 passer rating, which led the NFL coming into Sunday.

Lewis indicated he thought Dalton is the only player hurt Sunday that would miss next week's game.

WHIT BLAMES NFL FOR CHIPPY PLAY: It was as chippy as advertised. Even before the game. About 40 minutes before kickoff, Bengals WILL backer Vontaze Burfict left the stretch line and confronted Steelers linebacker Vince Williams at midfield.

A rugby-like scrum ensued with Steelers notorious enforcer James Harrison in the middle of it before it was broken up. There was pushing and shoving from the game's first snap and on the first drive of the game Steelers wide receiver Antonio Brown slapped Bengals cornerback Dre Kirkpatrick on the helmet after the play. When Kirkpatrick retaliated, both got flagged.

It will be recalled it was Williams who tweeted an off-season threat to Burfict in the wake of his season-ending tackle on Steelers running back Le'Veon Bell. Profootballtalk.com reported the tweet was deleted shortly after it went out last month.   

"That's the NFL's fault for not protecting the players," Whitworth said of the chippy game. "After he sent that tweet he should have been suspended or fined or they should have made a stand that you shouldn't do that. Making a threat off the field, in the street, and you do nothing about it in this in this day and age? If he made that threat to me, I've got four small kids and I've got to worry about this guy jumping me?

"It sparked everything," Whitworth said. "We're competitive and Bengals-Steelers has always been chippy. But what that almost turned in to was out of control. And it was an easy fix. You don't threaten another player's life off the field."

FIRST START: It has come to this. A win in AJ McCarron's first NFL start in San Francisco next Sunday can secure the Bengals' fifth straight post-season appearance.

After he threw for two touchdowns and two interceptions while completing 22 of 32 passes for 280 yards in the toughest of circumstances, McCarron showed why his head coach says the building has confidence in him.

"AJ did a heck of a job,' Whitworth said. "His passion, his accountability in the huddle. Quarterbacks all have different personalities, but he's got one of those rally-the-troop personalities. 'Just give me a chance, let me make this play,' type of guy. I think he's got that. It's a special thing not a lot of guys have and he has that. We'll see where he goes from here."

McCarron said he'll start preparing for the 49ers Monday at 8 a.m. watching tape at PBS with practice squad quarterback Keith Wenning. But he knows he needs the practice more than the film work.

"I don't want to make any excuses. I have to play better. Sometimes it's tough when you don't have one rep of your offense all week long. No matter how many times you watch film," McCarron said. "When you're young, you're going to have mistakes. You just have to have fewer and learn a lot faster when you're in this situation. It's what I've got to do and I'm up for it."

Next week marks the first time in nearly seven years, since Dec. 28, 2008, that a Bengals game has started without Dalton or Carson Palmer at quarterback. McCarron becomes head coach Marvin Lewis' fifth starting quarterback in 206 games, joining Dalton, Palmer, Jon Kitna, and Ryan Fitzpatrick.

REGGIE, REGGIE: For the fourth time, Bengals safety Reggie Nelson picked off Ben Roethlisberger in the fourth quarter. This time with 7:28 left off an acrobatic center-field tracker on a deep ball. But it's the first time the Bengals didn't win the game. It was also his NFL-leading eighth pick and tied two club records: most interceptions by a safety with David Fulcher in 1989 and five straight games with a pick to match Ken Riley in 1975. Nelson has now intercepted Roethlisberger six times for more than a quarter of his 23 Bengals interceptions, good for sixth place on the Bengals all-time list and two behind Lemar Parrish. DRE FUMING:Michael Johnson and Dre Kirkpatrick were two Bengals defensive players who said after the game they thought the Bengals lost their composure at times.

"We lost our cool a couple of times with what those guys were trying to get us to do," Kirkpatrick said. "We just have to stay consistent and continue to play together and continue to rely on each other."

Johnson said the Bengals, "Were not poised at all."

"They did a good job getting us out of focus. All that stuff after the whistle, that's not how you win games. When somebody is blocking you, that's when I try to be tough. All that other stuff is for the birds."

Amid all the talk of rallying around McCarron, Kirkpatrick said, "First we have to learn to be poised and lead by example for the young guys."

Kirkpatrick agreed with Whitworth that Williams should have been fined for threatening Burfict.

 "But we're not here to make excuses," Kirkpatrick said. "We knew what type of game it was. We knew it was going to be a hard-fought battle. They got the best of it today. We have to learn to play within ourselves and not feed into the things they're trying to do."

Kirkpatrick also said he thinks the refs should be miked and couldn't believe two calls.  One on third-and-seven late in the game when he was called for holding Steelers wide receiver Antonio Brown for an automatic first down. He said one of the refs told him it was a bad call.

"How is that possible? Kirkpatrick asked. "What did I do wrong? He's in my body."

He also was upset on the first drive of the game when Brown belted him in the helmet after the play and there was no 15-yard flag until Kirkpatrick retaliated with Brown hovering for off-setting penalties.

"He hit me in my face. You weren't going to call that flag if I had never responded," Kirkpatrick said. "I'm tired of that. You have to give us the respect that you give these whatever you want to call profile guys. He hit me first. When you go back and watch the tape, you'll see it. I kind of waited because I'm saying, is the ref going to throw a flag?  But he kept walking up to me." THIRD DOWNER:Steelers quarterback Ben Roethlisberger didn't throw a touchdown pass and didn't complete a ball longer than 31 yards. Tight end Heath Miller was their leading receiver with 10 catches for just 66 yards. And Pittsburgh ran for just three yards per carry on 28 tries.

That sounds like a Bengals win because they contained a Pittsburgh offense that came in averaging 529 yards in the last four games and had 354 on Sunday.

 But the killer is that Roethlisberger completed his first seven third-down passes for six first downs and 77 yards in staking them to a 13-7 lead and Miller had four of them as they nickel and dimed the Bengals underneath.

Despite the third-down chances (the Steelers converted eight of 14 and eight were third-and-five or longer), the Bengals' four-man rush couldn't get to Roethlisberger consistently. They sacked him twice and hit him four times in 39 passes. The result was a crushing edge in time of possession, more than 11 minutes.

"We lost the game on third down," said left end Carlos Dunlap, who did get a sack for a personal-best 10.5 on the season. "He was getting the ball out quick all day. I'd like to say we did a good job getting after him. He was just getting it out quick."

The banged-up Bengals secondary, which lost safety George Iloka early when he apparently re-aggravated his groin injury, held up against the deep ball with Leon Hall (back) and rookie cornerback Josh Shaw teaming with Kirkpatrick to hold the Mad Bomber Roethlisberger to 7.2 yards per throw.

Given that Roethlisberger is averaging 8.3 for the season, that's a good day's work, but Roethlisberger still had time to find his nooks and crannies. As usual, the Steelers max protected most of time on third down.

"When you have tight ends and backs hanging back and  chipping, that's going to happen sometimes,' said Michael Johnson, who had the other sack. "We were able to hit him and get him a couple of times. We could have got to him more. We'll look at the tape and see where we can get better."