They were known as the Cali Trio. They were supposed to be the ones that opened the door for Oklahoma to California.
But following the 2011 season, it started to feel like the Cali Duo and Clay. Stills and Jefferson were thriving and already making an impact, while Clay was hampered by injuries and buried on the depth chart.
His perseverance was one reason so many fans were thrilled for Clay in 2012 when he scored the game-winning touchdown in overtime against Oklahoma State.
Clay will never forget that moment. But as great as that one is for him, it's not the first thing he talked about when discussing his career highlights.
"It's up there. I'd say it's probably one of my favorite career moments," Clay said. "I personally liked to be a part of my first 100-yard game last year against Iowa State. I just felt that was more of a confidence booster."
That game was a turning point for Clay. He rushed for 157 yards on 24 carries and a touchdown. It was just a harbinger of things to come for Clay as a senior.
Not the most flashy, not the most explosive, Clay has made the most of his opportunities. That was never more apparent two weeks ago in a win at Kansas State. He rushed for a career-high 200 yards on 31 attempts with two touchdowns.
"I think Brennan is a guy that's been extremely consistent in who he was on and off the field," co-offensive coordinator Josh Heupel said. "He's got a great energy. He's been extremely positive for this program. He's been a great leader in the way he prepares every week."
Clay had a goal of rushing for 1,000 yards this season, but it didn't seem to be in reach a few weeks ago. He now stands at 843 yards on 134 attempts, averaging an impressive 6.3 yards per carry with six touchdowns. Not known as the home run hitter, Clay has three touchdowns of at least 63 yards this season.
The journey wasn't an easy one, which has made everybody in the program appreciate just how far Clay has come.
"Brennan has been a guy who has always been an opportunist," co-offensive coordinator Jay Norvell said. "When he wasn't a starter and he was a backup he still came into games and gave a monster performance.
"I think that is one legacy he will leave for the younger backs – to always be ready for your opportunity and be ready to take advantage of it."
The opportunities weren't always there. He had to battle a concussion, which he said really set him back in terms of his confidence. Then he went through a pinched nerve in his neck as a sophomore where there were some that thought he might end up being a mega-bust for a four-star running back ranked No. 6 at the position coming out of high school.
Clay was always grouped together with Stills and Jefferson. But with Stills and Jefferson both in the NFL, this season became about Clay. He has forged his own identity.
"It has been different," Clay said. "I always think what if they were still here. I miss them, and they tell me the same thing. We talk all the time, and I'm so excited that performing so well at the next level."
Their success never bothered Clay. When things weren't going his way early during his time at OU, all they did was encourage him.
"Them doing so well motivated me," Clay said. "We came here together and we were going to make plays together. I was happy that going into my junior year I was going to be able to be a part of that.
"I kept the faith and everything has worked out."
Clay said last year's Bedlam run was a once in a lifetime deal, something special. He hopes to make another special memory Saturday in Stillwater.