After spending the past 12 seasons with Missouri's staff, offensive coordinator and assistant head coach David Yost has resigned for personal reasons, the school announced Monday.
Yost had spent 17 seasons with Missouri coach Gary Pinkel, initially joining Pinkel's staff at Toledo as a graduate assistant in 1996.
"First off, I want to thank Coach Pinkel for an amazing 17 years," Yost said in a release through the school. "He has done so much for me and I'm just so grateful for the faith that he showed in me and all of the opportunities that he sent my way. I also want to thank Mike Alden for the support he has given me personally, and to our program. Mizzou is a special place, and I know that we're positioned to do great things going forward.
"There are a lot of factors that played into the process of coming to my decision. I feel like I've had a great run here and that it's just the right time to turn it over to someone else. On one hand, it's a really hard decision to make, but on the other hand, I feel good that it's the right decision at the right time for me.
"I'm going to miss our staff, they're like brothers to me, and not being around our players, that's hard to think about how tough that will be."
Yost's resignation comes after a season in which the Tigers went 5-7 (2-6 in conference play) in their first year in the SEC.
After owning one of the nation's most balanced offensive attacks during its last season in the Big 12 in 2011, Missouri ranked 11th in the SEC in total offense (356.4 yards per game) and scoring offense (25.8 points per game).
The 2012 season marked the first time since 2004 that Missouri's offense didn't average more than 400 yards per game.
Yost was a part of Pinkel's first staff at Missouri in 2001, when he served as quarterbacks coach and recruiting coordinator. Yost stayed in those roles through the 2008 season and was eventually promoted to offensive coordinator in 2009. He was then named assistant head coach in the fall of 2011.
Smith became the first quarterback in FBS history to throw for 8,000 yards and rush for 4,000 yards in a career. The Jacksonville Jaguars drafted Gabbert in the first round in 2011.
Current Missouri quarterback James Franklin enjoyed a breakout season in 2011, when he passed for 2,865 yards with 21 touchdowns and ran for 981 more yards and a team-high 15 rushing touchdowns. Behind Franklin's impressive play, the Tigers ranked fifth in the Big 12 in total offense (475.5) and scored 32.8 points per game. Missouri led the conference and ranked ninth nationally in rushing, averaging 244 yards per game. Missouri was also one of only two schools in the country to average at least 230 yards rushing and passing on the year.
However, a handful of injuries along the offensive line and to Franklin this season helped drop those numbers considerably. The Tigers averaged more than 100 fewer yards rushing each game and averaged just 217 yards passing.
Pinkel said he will search both nationally and internally for Yost's replacement, but no timetable has been set for the timing of the hire.
"It is very difficult to imagine not having David as part of our staff," Pinkel said in the school's release. "I asked him to reconsider, but I respect his decision. He has been such an instrumental part of our program and everything we've built since we came here. There's hardly an aspect of our program that he hasn't had a hand in, and we're going to miss his leadership and energy. He was responsible for a lot of things, and he did them all very well. He was an outstanding representative of Mizzou who busted his tail for our program. He's going to be tough to replace."