Rookie wide receiver A.J. Green caught a 41- 17 victory over the Cleveland Browns.
Green, the fourth overall pick, registered his first career reception and touchdown with the go-ahead score for the Bengals (1-0), who went 4-12 in 2010.
Gradkowski spelled injured rookie starter Andy Dalton to begin the second half and completed 5-of-12 passes for 92 yards. Dalton, the 35th overall pick out of TCU, went 10-of-15 for 81 yards and a touchdown before suffering an injured right wrist.
"He had some initial scans and all of them were negative, but we will have to see on whether he will be able to play next week or not," said Bengals coach Marvin Lewis. "We are hopeful that he will be able to, but I cannot tell you anymore right now and nor will he."
Cedric Benson rushed for 121 yards and a score on 25 carries.
Colt McCoy threw for 213 yards and two touchdowns against an interception on 19-of-40 passing for the Browns (0-1), who finished 5-11 a year ago and played their first game under new head coach Pat Shurmur.
Peyton Hillis carried the ball 17 times for 57 yards.
Gradkowski, signed by Cincinnati in the offseason, started under center to begin the third quarter. The Bengals went three-and-out and the Browns tacked on a 20-yard field goal from Phil Dawson on the ensuing drive to grab a 17-13 advantage.
Gradkowski struggled to make headway, as the Bengals punted on their next three possessions. But during a drive that started with 6:19 remaining in the fourth, the former Raider delivered.
The Bengals sprinted out of the huddle facing a 3rd-and-11. The Browns were caught off guard and were still aligning themselves as the ball was snapped. Green took advantage, releasing down the sideline past Joe Haden for the decisive score.
"Bruce actually came in and did what we expected him to do," said Lewis. "He did some things we would have like to get back, but I thought he handled the situation very well."
The Browns went three-and-out and elected to punt, then forced a Cincinnati punt, receiving the ball at their own 33-yard line with 3:17 remaining. McCoy completed a short pass to Hillis on first down before throwing two consecutive incompletions. His 4th-and-8 attempt fell incomplete near the line of scrimmage, marking a turnover on downs.
Benson reeled off a 39-yard touchdown run on the Bengals' next drive to cap the scoring.
"We had a situation where they made a big play on us," said Shurmur. "Once that happens, the game's not over. You've got to put yourself in position where you go down the field, you score and you win it."
The Browns' opening drive stalled after the three plays and, following a 20- yard punt by Richmond McGee, the Bengals took over at the Cleveland 41.
They leaned on Benson, who carried the ball five times during the drive, before taking a 3-0 lead on Mike Nugent's 24-yard field goal.
Following another Cleveland punt, Dalton engineered a seven-play, 41-yard drive which culminated in a two-yard touchdown strike to Jermaine Gresham.
The trend continued, as the Browns punted for the third time in as many possessions, and the Bengals took a 13-0 lead on Nugent's 47-yard field goal early in the second quarter.
From there, Cleveland jolted to life, reeling off 17 consecutive points.
McCoy began the surge with a 34-yard touchdown strike to Ben Watson over the middle. The Bengals then went three-and-out, but a holding call on Josh Cribbs' punt return placed the Browns at their own 10-yard line.
Facing a 3rd-and-7, McCoy scrambled nine yards for a first down. Hillis then reeled off a 17-yard run. On the following play, McCoy rolled to his right and heaved the ball off of one foot, connecting with Mohamed Massaquoi for a 56- yard completion. Evan Moore capped the drive with a touchdown reception, giving the Browns a 14-13 lead.
Dalton was hit by Browns rookie defensive tackle Phil Taylor on the Bengals' final offensive play of the half and appeared to favor his arm as he left the field.
Green went to the University of Georgia...On Sunday, the Browns reportedly signed defensive tackle Ahtyba Rubin to a three-year deal, according the Cleveland Plain Dealer.