ENGLEWOOD, Colo. -- With a first-team defense that still looks like it's the league's best and a running game that appears poised for an outstanding season with C.J. Anderson being relieved by emerging rookie Devontae Booker, the first job of the Broncos' starting quarterback is simple: Don't make the killer mistake.
Mark Sanchez and Trevor Siemian failed at that task on Saturday night. As a result, the Broncos' quarterback outlook remains muddled, although coach Gary Kubiak announced Monday that Siemian would start Saturday's preseason game against the Los Angeles Rams.
"We continue with the competition," Kubiak said.
While Kubiak has decided on his No. 1 quarterback for Saturday, he won't choose the Week 1 starter until next week, before the preseason finale at Arizona. And he doesn't yet know who will be the second quarterback in against the Los Angeles Rams this Saturday; all he knows is that he plans to give Siemian, Sanchez and rookie Paxton Lynch equal work.
Whether that means Lynch gets some first-team work is perhaps the biggest question. Although Lynch has looked raw at times, he has adjusted to the speed of the rush and gotten more comfortable with every series in the games he's played. He's also the only one of the three quarterbacks to lead two touchdown drives in the preseason, and he's displayed an innate feel for escaping the rush while squeezing the ball into tight windows.
"I think Paxton has done some good things. The other night he got off to a slow start, but he finished extremely strong," Kubiak said.
Siemian looked sharp in the first quarter in making his initial professional start of any type. He hit nine consecutive passes, showed improvement at going through his progressions and moved the offense to a first-drive touchdown.
Then, on the first play of the second quarter, he locked in on Demaryius Thomas to his right. San Francisco's Eric Reid read it perfectly, and stepped in front of the pass for a 42-yard touchdown.
Sanchez entered in the second quarter after Siemian. Just like the starter, he settled into a groove, working the edges and the seams. Then he fumbled under pressure, and after getting a reprieve when backup linebacker Zaire Anderson forced a fumble, lost another fumble on the subsequent series.
Those were the second and third turnovers by Sanchez in just two quarters of work in the preseason, and given his proclivity for giveaways in his first seven seasons, only serve to reinforce the pre-existing perception of him: that he's good enough to give you a chance, but sloppy enough with the football to fritter it away.
He was crestfallen after the game.
"That's Mark. He's a competitive guy. He talked about opportunity," Kubiak said. "That's the type of guy you want out there battling every day."
But what Kubiak wants most from his quarterbacks is to protect the football. Of the three, Siemian does that best, based on his play in training camp. And while he didn't test the 49ers downfield -- none of his passes were caught more than 12 yards from the line of scrimmage -- he kept the chains moving, and is only responsible for one turnover this summer.
That, above all, is why Siemian gets another shot with the starters -- and why he could be in pole position to be the starter against Carolina, despite having never thrown a regular-season pass.