He spent a large portion of practice speaking injured offensive guard Desmond Wynn, had lunch with a few members of the offensive line and met with coach Greg Schiano for nearly two hours.
And when the day was done, the 6-foot-6, 290-pound Muller, who was offered by Rutgers in the summer, also said he had a top five.
Muller already thought highly before his day-long visit, which included watching a scrimmage, and being able to spend time talking with the offensive linemen helped greatly.
"I liked it," Muller said. "I liked being able to talk to players and see how Schiano holds scrimmages. I was talking to (Wynn) and 1-on-1 and seeing what he had to say. It's a big family. It's like one big melting pot."
Muller appreciated it because it was a side of the program he was yet to experience, although members of the Scarlet Knights' coaching staff explained it during the recruiting process.
"I never got to see it in person," Muller said. "Desmond was really serious about everything. He was telling me things straight up, which I enjoyed. He was not afraid to show what school is about."
Muller's day began with a 6:30 a.m. wake-up call and drive to campus, where he sat in during the offensive line meeting.
"I sat in with (offensive line) coach (Kyle) Flood, and it was cool," he said. "I Got to see he's real passionate, even at 8 a.m."
He also spent time watching the offensive line warm up before the scrimmage.
"I like flood," Muller said. "I like what he's doing, how he treats his lineman. He treats then with respect. And they were taking about the offensive line going out to dinner (Tuesday) night."
After the scrimmage, Muller went with some of the offensive linemen to the Grease Trucks, where he downs a trio of "Fat" sandwiches before heading back to the Busch Campus to meet with Schiano.
"He was talking about wanting me, and how they would have a scholarship for me no matter when I made a decision," Muller said. "He said it would help if I commit now because I could help with recruiting class."
Muller said he wanted to make a decision before the start of his senior season.