This game turned on a dime. Or, actually, a fumble.
With Northwestern driving for a go-ahead score in the second quarter, Treyvon Green coughed it up at the Michigan State 3-yard line. The Spartans responded with a 97-yard touchdown drive and never surrendered the lead, winning 31-17 at windy and soggy Ryan Field.
Northwestern, which was shooting for a fifth consecutive victory, finished the regular season 6-6 (3-5 Big Ten) and will await its bowl fate. Michigan State improved to 10-2 (7-1) heading into next Saturday's inaugural Big Ten championship game.
Three plays actually defined this game: the Green fumble, cornerback Jordan Mabin's shoulder injury and Brandon Williams' rugby punt just before halftime. It was short and low and bounced into the arms of Keshawn Martin, who cut right into daylight and brought it back 57 yards without being touched.
Mabin's injury was huge because Northwestern replaced him redshirt freshman Daniel Jones. Michigan State picked on him repeatedly.
Jones had decent coverage on a perfect 47-yard Kirk Cousins completion to Martin in the second quarter, but Martin out-fought him for the ball. On the next play, Le'Veon Bell juked Jones for a 7-yard touchdown.
Cousins hit B.J. Cunningham for a 33-yard strike in the third quarter with Jones in coverage.
And with the Spartans leading 24-17 with less than six minutes to play, Jones was one-on-one with Cunningham, who bobbled Cousins' throw but held on for the touchdown. Cousins became Michigan State's all-time leader in touchdown passes, with 62.
Like earlier in the season, NU's secondary was too flawed against a top-notch passing attack.
After starting 1-for-4 for nine yards, Cousins completed 13 of 16 passes for 205 yards.
Dan Persa played valiantly in his final home game, escaping Michigan State's fierce pass rush multiple times. In his final home game, Persa completed 23 of 32 passes for 245 yards, two scores and no interceptions. He was sacked six times.
tgreenstein@tribune.com
Twitter @TeddyGreenstein