By Joey Kaufman | [email protected] | Orange County Register PUBLISHED: October 13, 2018 at 7:40 pm | UPDATED: October 13, 2018 at 7:40 pm LOS ANGELES — USC will be without senior linebacker Cameron Smith against No. 19 Colorado on Saturday night. Smith, the veteran presence in the middle of the Trojans’ defense, was ruled out because of a mild hamstring strain, a team spokesman confirmed. The senior strained his hamstring during practice on Wednesday, forcing him to leave early, and he also missed practice on Thursday. Afterward, Coach Clay Helton described Smith as “50-50 at best” to suit up against the unbeaten Buffaloes, casting some doubt on his availability for the critical Pac-12 South contest. True freshman Palaie Gaoteote was announced as a starter in place of Smith. Gaoteote, a highly touted recruit from Bishop Gorman High in Las Vegas, previously started in place of outside linebacker Porter Gustin last month when Gustin was suspended for the first half because of targeting. Outside linebacker Jordan Iosefa could also fill in for Smith at the “Mike” linebacker position. Smith did not go through warm-ups before the game against Colorado. He was wearing his jersey over a sweatshirt and sweatpants on the sideline. Smith had not missed a game since the end of his freshman season in 2015 when he tore his ACL. The Trojans leading tackler, he had appeared in 32 straight games since then, starting 31 of them.