McGruder scored 21 points, Irving forced 10-second and 5-second calls against TCU players and the 16th-ranked Wildcats stretched their winning streak to seven games with a 67-54 victory over the Big 12 newcomer Wednesday night.
"It is fun, a lot of movement, not really set plays, so it's hard to learn," McGruder said. "I like the confidence everyone has."
The Wildcats (14-2, 3-0 Big 12) got off to a slow start before taking control with a 19-4 run midway through the first half.
McGruder's layup with 11 minutes left in the first half tied the game at 10, after Kansas State had fallen behind 10-5. The Wildcats led for good when McGruder had a defensive rebound and turned that into a fastbreak 3-pointer by Will Spradling. A floater by McGruder stretched the lead to 24-14.
"We came out a little lethargic. Our bench did a great job, our seniors did a great job of leading us and giving us the energy we needed. ... Rodney gets going," Weber said. "It's a good win."
Kansas State gets to go home for games against Oklahoma and No. 4 Kansas, the other teams off to 3-0 starts in the Big 12.
Adrick McKinney had 18 points and nine rebounds for TCU (9-8, 0-4). Kyan Anderson had 10 points on 4-of-11 shooting.
When the Horned Frogs cut the gap to five points with a chance to get closer before halftime, they started making mistakes.
"I thought we played probably as about as good as we could play for about the first 3 or 4 minutes," first-year TCU coach Trent Johnson said. "But like most good teams that are mature, skilled, understand their roles—we had a couple breakdowns defensively, we had a couple breakdowns offensively—and they make you pay."
Connell Crossland had a steal and passed to Anderson, but TCU's top scorer missed a layup after getting himself in an awkward position under the rim. Irvin then hit a 3-pointer for Kansas State. Anderson had a turnover that led to a 3 by McGruder.
When TCU freshman Clyde Smith III was called for a 10-second violation, unable to get the ball past midcourt while being defended by Irving, McGruder drove for a high bank shot and a 34-21 lead that matched Kansas State's biggest of the half.
"The past few days Coach has been on me how I've been playing defense lately," Irving said. "I wanted to come out and make a statement in this game."
In 18 minutes off the bench, Irving had eight points, five assists and three steals.
While McGruder finished with 9-of-15 shooting with three 3-pointers and was the only K-State player in double figures, although three others scored eight points. One of those was Jordan Henriquez, who had 10 rebounds.
TCU got the first basket after halftime when Devonta Abron scored, but McGruder responded with a 3-pointer and Spradling hit another from long range.
The Wildcats are two wins shy of matching the 16-2 mark they had three seasons ago that is their best start over the past 25 years. They have won their last five conference road games, dating to last season.
Kansas State and TCU played for the first time since a 1999 NIT game the Horned Frogs won. They had played five times previously, TCU winning that NIT game and another in the 1968 NCAA tournament while the Wildcats had won all three regular-season meetings.