Kentucky spent much of the game struggling to find a playmaker to replace Dicky Lyons Jr., out for the season because of torn ligaments in his right knee. But Cobb, wearing Lyons' No. 12 as a tribute, did his best impersonation of the senior receiver when it mattered.
Kentucky (5-2, 1-2 Southeastern Conference) trailed the whole game until Hartline connected with Cobb from 21 yards out with just over 2 minutes left. Cobb cut through the middle of the field untouched and Lones Seiber's extra point was good, giving the Wildcats their final margin.
Marcus McClinton's interception in the final seconds allowed the Wildcats to run out the clock.
Cobb, the backup quarterback and a fan favorite to take over from Hartline under center, asked to wear Lyons' No. 12 before the game. Although he got a few snaps at quarterback, his play at receiver boosted the Wildcats most.
A few minutes before catching the winning score, he ran in from 32 yards out, and a Kentucky passing game that had been dormant most of the year showed life.
The loss for Arkansas (3-4, 1-3) was the first against the Wildcats for Petrino, the former Louisville coach who had beaten them four straight times with the Cardinals.
Hartline completed 17 of 32 passes for 239 yards, three TDs and two interceptions. Besides Cobb, he also connected with Alfonso Smith for a 71-yard score -- the Wildcats' longest play of the season.
Smith and Cobb each had five catches.
The comeback ruined a huge performance by Arkansas' Michael Smith, who scored twice and had a career-high 192 rushing yards. After toiling two years behind first-round NFL draft picks Darren McFadden and Felix Jones, Smith has distinguished himself as their successor against some of the Southeastern Conference's top defenses.
Coming into the game, Kentucky had been stingy against the run, allowing just one rushing TD all year. But Smith put a quick end to that with a 2-yard spin into the end zone.
On the next drive, Smith flashed his breakaway speed with a 51-yard sprint through the middle of the field. He showed similar abilities as a receiver before halftime, reeling in a pass from Casey Dick in the flat and taking it 23 yards untouched make it 14-0.
For the first time all year, Kentucky won a game with its offense, not its potent defense.
In the first 20 minutes of the second half, Kentucky ran just six plays. Other than that, Arkansas chewed up clock, with a combination of its running game and several costly Kentucky penalties and mistakes, even though they only had two field goals to show for it.
First, an Arkansas punt bounced off the foot of Kentucky's DeMoreo Ford, giving the Razorbacks the ball at the 7. Shay Haddock's 19-yard field goal attempt got a fortunate bounce, ricocheting off the left upright before falling through.
Then came an 87-yard field goal drive that seemed to never end. Arkansas consumed nearly 10 minutes on the drive, using 20 plays. The teams were penalized six times on the drive.
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