WEST LAFAYETTE, Ind. -- Fifth-year senior quarterback John O'Korn, a transfer from Houston, came off the bench during the first quarter when starter Wilton Speight was injured and led No. 8 Michigan to a 28-10, come-from-behind victory against Purdue on Saturday in sold-out Ross-Ade Stadium.
O'Korn, through Michigan's first three games, had completed his one pass attempt for 37 yards.
After Speight's head injury with 5:06 left in the opening period, O'Korn led four touchdown drives, completing 18 of 26 passes for 270 yards and one touchdown.
Chris Evans' 49-yard touchdown run with 6:46 to play -- his second TD of the afternoon -- completed a 21-0 Michigan second-half blitz and helped the Wolverines (4-0, 1-0) remain unbeaten. Evans rushed 14 times for 97 yards.
Michigan had stretched its lead to 21-10 with 10:36 remaining on Ty Isaac's 1-yard run, capping a nine-play, 65-yard drive that included O'Korn completions of 23 and 14 yards that moved the ball to the Boilermakers' 3-yard line.
The Wolverines seized a 14-10 lead with 2:42 to play in third quarter on Evans' 10-yard run, completing a methodical 11-play, 86-yard drive that included O'Korn's 30-yard completion to Sean McKeon to the Purdue 37 and a targeting penalty.
Michigan took a 7-0 lead with 11:34 remaining in the second quarter on O'Korn's 12-yard pass to tight end Zach Gentry, capping a 13-play, 84-yard drive.
On the ensuing drive -- Elijah Sindelar's first after replacing starting quarterback David Blough -- Purdue (2-2, 0-1) drove 75 yards in five plays, pulling even at 7 on Sindelar's 10-yard touchdown pass to tight end Brycen Hopkins with 9:45 left in the half.
With 8:15 remaining in the second quarter, Boilermaker safety Navon Mosley intercepted O'Korn at the Wolverines' 27. J.D. Dellinger's 29-yard field goal at the 6:04 mark pushed Purdue into a 10-7 halftime lead.
The Boilermakers out-gained the Wolverines 179-131 during the first 30 minutes, including 99 passing yards from Sindelar on 6 of 12 attempts. Blough was 3 of 7 for 11 yards during the four first-half drives he directed.
NOTES: Purdue rushing leader Tario Fuller (43 rushes, 261 yards in three games) did not dress because of an ankle sprain. ... Game time temperature was 89 degrees, the warmest in Ross-Ade Stadium since a 2011 game against Middle Tennessee State, when the temperature at kickoff was 90. ... The sellout crowd of 60,042 was Purdue's first home sellout since 63,107 -- the pre-renovation capacity -- watched the Boilermakers defeat Indiana on Nov. 22, 2008, in former coach Joe Tiller's final game at Purdue. ... Boilermakers S Jacob Thieneman was ejected for targeting with 4:38 remaining in the third quarter, driving his shoulder pads into the helmet of Michigan receiver Nick Eubanks. ... Purdue LB J'Whaun Bentley was ejected for targeting with 11:20 left in the fourth quarter.