"I believe it's my job to lose," the incumbent said Friday at the team's preseason media gathering, "and I'm not going to lose it."
Indeed, some conspiracy buffs contend London has assured Sims the gig. After all, they theorize, Sims didn't leave the reigning national champion Crimson Tide, where he was AJ McCarron's backup in 2011, to be an understudy at Virginia.
Believe what you must, but that doesn't compute.
No coach can afford to award the sport's most critical position out of blind loyalty. It's a certain formula for losing games, the locker room and your job.
With his improvement on the field and presence off the field, Rocco, a junior, has earned the locker room's respect. Not to suggest he's Andrew Luck, Matt Barkley or Logan Thomas. He's not. He ranked eighth among ACC quarterbacks last season in pass efficiency.
But Rocco did improve markedly. He engineered a last-ditch, 75-yard drive that produced the winning touchdown at Florida State. He threw for a career-best 312 yards in the Chick-fil-A Bowl loss to Auburn.
"He's a guy you can count on," tailback Kevin Parks said. "He's a guy who's always doing the right thing."
"You look at last season," offensive tackle Morgan Moses said. "Rocco got better day in and day out."
And how did Rocco respond last month to the news that, thanks to an NCAA hardship waiver, Sims is eligible this season?
"He took it like a man," Moses said. "He got better."
Rocco's best last season came after London and Lazor stopped alternating him with freshman David Watford of Hampton. The change sparked road victories over Miami, Maryland and Florida State that propelled the Cavaliers to an 8-5 record, their best since 2007.
"For me, it's always a competition," Rocco said. "I felt like when (Sims) came in really nothing changed from my point of view. I believe I'm the starting quarterback and the leader of this team. … I believe (the players) think of me as the leader of this team, too. They tell me that. They reassure me."
Given the complexity of Lazor's pro-style offense and the short preparation time, my hunch is Rocco starts the opener Sept. 1 against Richmond, coached by Rocco's uncle, former Virginia assistant and Liberty big whistle Danny Rocco.
But Rocco had better produce, and quickly. If not, Sims or Watford will take over as the Cavaliers tackle consecutive tests against Penn State, Georgia Tech and Texas Christian, the latter two on the road.
"I don't know what will happen," Lazor said. "I don't have an opinion today because I don't have to. So I'll just let it play. It's hard enough when you have to decide."
Neither Lazor nor London wants a repeat of 2011's uncertainty. They want to enter the season firm and confident in their choice.
That choice was clear until Sims arrived with three seasons of eligibility remaining. A consensus All-American at Chesapeake's Oscar Smith High, he set state records for career passing yards (10,725) and touchdown passes (119), and led the Tigers to the 2008 Division 6 state championship.