Coach Gary Patterson made the announcement Tuesday, five days after the junior starter was arrested on suspicion of drunken driving in his second brush with the law in the past eight months.
Patterson said most of the inpatient programs like the one Pachall will enter are 30 to 60 days. If Pachall completes the treatment, the door remains open for him to come back to school and the team.
"Hopefully, what our plan is that he (Pachall) gets himself right and keeps the door open for us as far as an opportunity for him to be able to come back here and enroll in the spring," Patterson said. "He would be able to graduate in two semesters, which is the ultimate goal for us. Also, we'd get a great kid and also a good quarterback back."
Pachall was arrested on suspicion of driving while intoxicated after running a stop sign near the TCU campus last Thursday. That came eight months after Pachall admitted to police that he smoked marijuana and failed a team-administered drug test just two weeks before former linebacker Tanner Brock, his roommate and teammate then, was arrested in a drug sting with three other players and other TCU students.
Patterson said he met with Pachall and his parents and everyone agreed that he needed time away from school and football to get his life back on track.
"There was only one way he was going to change the path that he was on," Patterson said. "And that was he just needed to step away from it all. I think it's the best decision for this football team and Casey Pachall."
When Pachall's failed drug test was revealed publicly in a police report just before the start of preseason practice in August, the quarterback wasn't suspended. Patterson said then that Pachall had completed drug and alcohol counseling mandated by the university.
Patterson said that he and his wife, Kelsey, will donate $100,000 to the TCU Recovery and Support Group, a drug and alcohol organization on campus that started in the fall.
"We want take this an opportunity to turn this into a positive where others can be helped," Patterson said.
Pachall threw for 948 yards with 10 touchdowns and one interception in TCU's first four games this season. The suspension of their second-year starter comes in the middle of the Frogs playing their first season in the Big 12 Conference and facing a difficult schedule the rest of the way.
Filling in for Pachall, redshirt freshman Trevone Boykin was 23-of-40 passing for 270 yards with a touchdown and three interceptions in Saturday's 37-23 loss to Iowa State. That ended the Frogs' FBS-best 12-game winning streak and knocked them out of the Top 25.
"We're still going try to win football games," Patterson said. "We won them before Casey Pachall was our quarterback and we're going win games after Casey Pachall is the quarterback."
The Horned Frogs (4-1, 1-1 Big 12) play at Baylor (3-1, 0-1) on Saturday, then face Texas Tech and Oklahoma State before consecutive games against four ranked teams currently with a combined record of 17-2. They will have to play at No. 5 West Virginia, before hosting No. 6 Kansas State, then going to No. 15 Texas and closing the regular season at home against No.13 Oklahoma.
"We're not panicking," TCU junior receiver Josh Boyce said. "We still have a whole season in front of us. We're looking forward to these next games."
Before the start of fall practice in August, Pachall said he needed to have the same expectations off the field that he did when he was playing.
"I know I'm not perfect," Pachall said at the time. "But I've learned from those mistakes and I'm still learning. It's a day-to-day process for me of trying to be a better person."
Last season, after replacing TCU's winningest quarterback Andy Dalton, Pachall set single-season school records with 2,921 yards passing and 228 completions. He threw 25 TDs with seven interceptions while the Frogs won 11 games, including a victory over Louisiana Tech in the Poinsettia Bowl.
While Boykin had been the backup quarterback the first four games, he was working out at tailback last week before Pachall's arrest changed things. Sophomore Matt Brown, Pachall's backup last season who had been moved to receiver, is now back in the quarterback mix.
Boyce said he was impressed how Boykin played against Iowa State on short notice.
"He had complete control of the huddle and did what a quarterback should do," Boyce said. "I think he'll be great. He'll have a whole week of practice and we'll help him out a lot."