Gaines became a full-time starter in 2021, and started games at each of the three line positions (tackle, guard, center). He played a major role in Zach Charbonnet's 1000-yard season that year, as well as the school's leading of the Pac-12 Conference in rushing yards-per-game. As a senior in 2022, he was key in Charbonnet's second 1000-yard season and helped UCLA lead the conference in yards-per-carry. A starter in every game, Gaines also appeared on all 932 snaps at right guard, and was a member of a line that was a semifinalist for the Joe Moore Award. He was an honorable mention all-conference choice and announced after the year that he was foregoing his final year of eligibility to enter the NFL Draft and play in the NFLPA Collegiate Bowl. He finished his stint at UCLA having appeared on 2,382 snaps, and only allowed five total sacks and 52 pressures.
