There was no good reason to see this coming. Sure, Illinois rode its first Big Ten winning streak in nearly two months into the Breslin Center. No doubt, those two straight victories, and three consecutive games holding their opponents under 50 points, were impressive. They might even have changed the book on this Illini team — from a story of disappointment and gloom to a tale of resilience and hope, would be one admittedly cornball way to put it. But this, a 53-46 mugging of big, bad Michigan State on its home turf? This was the Illini’s defensive gem of the season. This was the Gang That Can’t Shoot Straight tickling the twine at a far greater success rate than the normally sure-firing Spartans. This was the Illini keeping their cool for nearly all 40 minutes of their biggest victory of the season — one that quite possibly locks them into ­postseason play. Don’t even try to say you saw all that coming. “Coach [John] Groce’s mind-set has been to be positive all year,” said center Nnanna Egwu, who was a one-man wrecking crew at the defensive end. “He told us not to be scared coming in here.” You know who probably doesn’t buy a word of that? Tom Izzo. After this massively frustrating loss for his 18th-ranked team — whose roster was at full strength for the first time since Jan. 4 — the iconic MSU coach made it clear the result was all about his team, not about Groce’s. “We had a complete meltdown,” was one of Izzo’s gems. “I thought our energy level was at an all-time worst,” was another. The Illini are feeling good about themselves, anyway. Foolish? Not at all. They should feel good. Just like that — with three upset W’s in a row — they’re threatening to save their season. At 17-12 overall and an almost respectable 6-10 in Big Ten play, they have a very real shot at the NIT. And you’d better believe Illini fans were shooting higher than that as soon as this game was over. What they all want to know: If Groce can coax victories over Michigan and Iowa to finish the regular season, might the NCAA tournament become an actual possibility? It’s getting difficult for the players to keep their minds from drifting to that subject, too. “Yeah, it is,” said freshman Malcolm Hill, who had another solid outing with 10 points and five ­rebounds. “I’m not going to lie.” The Big Dance — who would have dared bring that up just one week ago?