Two Saturdays ago, Michigan State was the Big Ten’s only undefeated team.But with three losses in their last four games, it has taken a mere fortnight for the 11th-ranked Spartans (19-5, 10-3) to tumble into third place. It doesn’t get any easier for coach Tom Izzo and Co. as they face Illinois (17-8, 9-6) on Saturday night in Champaign, Ill.”I tried to explain when we were 9-0 (in the Big Ten) what was going on,” Izzo said. “I haven’t changed one bit. I told you four or five losses would win the league. I haven’t changed on that at all. We put ourselves in a hole now because we didn’t do the job at home. You’ve got to win your home games and split on the road.”With that formula percolating in everyone’s heads, a lot of Michigan State luminaries showed up in East Lansing, Mich., Tuesday night in anticipation of Izzo breaking Bob Knight’s record for most conference wins by a Big Ten coach.Instead, Indiana — Knight’s former school — kept Izzo stuck on 353 victories with an unexpected comeback inspired by something Knight abhorred — playing zone defense. Though the Hoosiers had played almost no zone previously this season, they switched to it late in the first half. Michigan State responded by shooting 4-of-23 from 3-point range.”We haven’t run into much zone,” Izzo said. “But when you run into it, your shooters gotta make shots.”Zone defense seems like a natural response to Michigan State’s season-long perimeter shooting woes. The Spartans enter Saturday’s game hitting just 28.8 percent on 3-pointers and converting just 5.6 threes per game.The percentage ranks the Spartans among the bottom 10 teams in the country, and no power-conference team is worse. Jaden Akins (team-leading 13.4 points per game) has made the most 3-pointers this season for Michigan State (36), albeit on just 29.3 percent shooting from long range.Fortunately for the Spartans, Illinois coach Brad Underwood prefers using a man-to-man to force opponents to get off the 3-point line and take tough mid-range shots.