CLEVELAND - Carson Palmer only needed one half to put away the badly bruised Browns.

Palmer threw four touchdown passes -- three in the second half -- and for 374 yards as the Arizona Cardinals rallied for a 34-20 win Sunday over the Cleveland Browns, who lost two defensive starters with concussions.

Palmer had two TD passes in the third quarter when the Cardinals (6-2) overcame a 20-10 halftime deficit. His third TD of the second half, a 6-yarder to Larry Fitzgerald, gave Arizona a 31-20 lead.

Michael Floyd had a 60-yard TD catch and tight end Troy Niklas had two short TD receptions as the Cardinals overcame four turnovers and won in Cleveland for the first time since 1985.

The Browns (2-6) dropped their third straight, and cornerback Joe Haden and safety Donte Whitner sustained concussions on consecutive plays in the third quarter, when Cleveland lost two defenders and the lead in a span of 7:25.

Quarterback Josh McCown had three TD passes. The 36-year-old also played much of the second half in pain after re-injuring his right shoulder and ribs.

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After beating Baltimore on Monday night, the Cardinals had a short week to prepare for their trip to Cleveland, and for long stretches they seemed ill-prepared. An early fumble by running back Chris Johnson helped the Browns build a 20-7 lead in the first half before Palmer and his teammates snapped out of their funk.

Chandler Catanzaro kicked two field goals for the Cardinals, who outscored the Browns 24-0 after halftime.

Arizona scored on its first two possessions of the third quarter as the Browns began to break down.

Floyd got behind Haden down the right sideline and hauled in a pass from Palmer, who just missed connecting on several long throws in the first half. Haden tried bring down Floyd with a late dive, and then got up slowly before staggering to Cleveland's sideline. He missed the Browns' two previous games with a head injury.

Still trailing 20-17, the Cardinals then took the lead on Palmer's 1-yard toss to Niklas. On that drive, Whitner got rattled while tackling wide receiver Jaron Brown on a 39-yard gain.

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McCown barely made it through the game. He missed practice time this week with a sore right shoulder and ribs, injuries sustained last week in St. Louis, and was questionable to play. In the third quarter, he took a hard hit from linebacker Kevin Minter and grimaced as he got off the field before dropping to a knee. He was examined by trainers and returned to the game.

McCown, though, bent over several times as he fought the pain, and at one point he waved off Cleveland's coaches and backup Johnny Manziel, who finally came in with 2:16 left and may have to play Thursday night in Cincinnati.

McCown threw three TD passes in the first half -- all on third down -- as the Browns opened a surprising 13-point lead over the Cardinals, who came in as the NFL's second-highest scoring team and with one of the league's most balanced offenses.