There is a big hole to fill on the left side of the Colorado offense for the second time in three years and few options to evaluate as spring football began Thursday afternoon.

The two most likely candidates to replace David Bakhtiari at left tackle are out with injuries this spring.

Last season Alexander Lewis played left guard next to Bakhtiari, a two-time, second-team All-Pac-12 Conference selection who chose to turn pro instead of returning for his senior season. But Lewis won't be fully recovered from shoulder surgery until sometime in May.

Sophomore Marc Mustoe earned a handful of snaps as a redshirt freshman backup in 2012, but he will miss most of the work this spring with concussion symptoms lingering after being hit by a truck while riding his bike in January. He wasn't wearing a helmet.

CU’s Marc Mustoe.
CU's Marc Mustoe. ( CLIFF GRASSMICK )

The 6-foot-7, 290-pound product of Arvada West High School was riding his mountain bike home from a workout on campus at about 7 p.m., on Jan. 21 when he was hit by a Chevy Tahoe on Baseline Avenue. He never saw the SUV coming and the driver didn't see him. He was on his bike one minute and in an ambulance the next.

"I left a huge dent in that thing," Mustoe joked Thursday afternoon before meetings and practice.

No timetable has been set for Mustoe to be cleared to participate fully in practices this spring. He said he believes he will be able to join the competition to replace Bakhtiari at some point this spring. He was told after the accident that police estimated the Tahoe was traveling approximately 30 mph at impact. He believes he hit his head on the car and not necessarily the ground.

"I'm really glad I'm the size I am I guess cause I feel like if it was anyone else, it could have been really dangerous," Mustoe said. "I'm fortunate I guess to be alive. I don't know.

"God was definitely looking out for me."

While Lewis and Mustoe are the most likely candidates to man the left side next fall, for now CU coaches will make due with junior Jack Harris practicing on the left side after playing either right tackle or right guard last year. CU coaches are likely to move sophomore Stephane Nembot to right tackle for now.

Harris spent his first two seasons at CU practicing at left tackle behind former All-American Nate Solder, who became a first-round draft pick three years ago. Harris said left tackle has always been a natural position for him but he believes he will ultimately end up back at guard once all his teammates recover.

Harris missed most of the 2011 season with a leg injury but returned to start 11 of 12 games in 2012 at right guard or tackle. He said he is looking forward to the opportunity to play the left side this spring.

"I'll play there if I have to, if (Lewis) is not ready to go and if I earn the spot," Harris said.

Mustoe, a former four-star recruit, has been waiting patiently behind Bakhtiari the past two seasons as a freshman and redshirt freshman while working to get stronger and improve his technique. Now that his opportunity to possibly move up the depth chart has arrived, he is frustrated to be limited with spring drills starting.

"That's really hard because I want to be out there," Mustoe said. "I want to be competing. I want to be playing. I want to be working out. I want to do all the stuff that I'm not really allowed to, but I guess it's kind of like what coach MacIntyre is saying. If you can't go over, you go under. If you can't go around it, you go through it. You find a way to get it done and it doesn't matter what gets in your way. You've got to keep going. ... When I get back, I think the victory will be even more sweet."

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