EAST LANSING, Mich. (AP) -- Denicos Allen returned a fumble 45 yards for a touchdown, and Michigan State's offense finally added an insurance score in the fourth quarter of a 14-0 win over Purdue on Saturday.
The Spartans didn't make it past the Purdue 32-yard line until the fourth, when receiver Tony Lippett threw a 5-yard touchdown pass to Andrew Gleichert on a trick play.
Michigan State (6-1, 3-0 Big Ten Conference) remains atop the Legends Division but clearly has work to do with the toughest part of its schedule still to come. Purdue (1-6, 0-3) kept it close after being routed by Wisconsin and Nebraska in its first two conference games, but Paul Griggs missed two field goals.
The Spartans entered with the nation's top-ranked defense, and Allen opened the scoring in the second quarter with Michigan State's fifth defensive touchdown of the season. Max Bullough hit quarterback Danny Etling, the ball popped free, and Allen was able to scoop it up and score easily.
Purdue converted a fourth down thanks to a penalty, which gave the Boilermakers the ball at the Michigan State 34 with 9 seconds left in the second quarter. That was as far into opposing territory as either team advanced the ball in the first half, but Griggs was short on a 51-yard field goal attempt.
Griggs also came up short from 41 yards in the third quarter, and Michigan State scored again in the fourth. Connor Cook completed a pass to Macgarrett Kings for 25 yards on third-and-12, and a 26-yard catch-and-run by Josiah Price put the ball at the Purdue 7.
Two plays later, Lippett took the ball on what looked like an end-around, but he threw to an open Gleichert for a touchdown.
Cook went 13 of 25 for 107 yards, although at one point he had only 17 yards on eight completions. Etling was 14 of 25 for 160 yards, but he also threw a crucial interception in the end zone in the first quarter, after Purdue had reached the Michigan State 37 with a fourth-down conversion.
Jeremy Langford had 131 yards on 24 carries for Michigan State.
While the Spartans were sputtering offensively, punter Mike Sadler gave them a lift, landing three punts inside the 10-yard line.