Objective No. 1 for 49ers: Get through Broncos game without another QB injury

ENGLEWOOD, Colo. -- The San Francisco 49ers play their second preseason game Saturday night against the Denver Broncos after a pair of joint practices with them this week. Kickoff is set for 9 p.m. ET from Sports Authority Field at Mile High.

Here's a look at five things to watch from a 49ers perspective in this second preseason contest:

1. A close eye on the quarterbacks: Obviously the quarterback competition has dominated the conversation about the 49ers this preseason, and for good reason. But things are a little different at the moment because of the absence of Colin Kaepernick and the season-ending injury to Thaddeus Lewis. The Niners added Christian Ponder this week and expect him to play with less than a week in the system under his belt. The real conundrum is what to do with starter Blaine Gabbert. It stands to reason he'll get more reps this week than he did last, but the 49ers must also protect him because of the uncertainty with Kaepernick. San Francisco believes Kaepernick could be back practicing next week but have no guarantees on that front, so an injury to Gabbert would be a devastating blow. So they'll have to strike the right balance between getting him much-needed work and making sure he's not put in danger by being on the field for too long.

2. On the run: First and foremost, the 49ers want to be a successful running team under coach Chip Kelly. They were able to do that in the preseason opener against Houston, running for 236 yards. It was a good start, and it was particularly encouraging to see backs other than just starter Carlos Hyde doing the damage. Mike Davis led the way with 72 yards on five attempts, but San Francisco also got 61 yards on the ground from quarterback Jeff Driskel. Denver's defense figures to provide a stiffer test but if the Niners can continue building on their strong start on the ground, it should only make life easier for whoever is at quarterback when the season starts.

3. Changing of the guard?: The 49ers tinkered with the offensive line for a little bit in Thursday's practice, giving tackle Anthony Davis a chance to move inside to guard for the first time in his NFL career. Davis took limited reps at right guard in place of Andrew Tiller and said after that he volunteered for the job because he thought it might allow the team to get the best five offensive linemen on the field. Davis also said he didn't expect to play guard against the Broncos, but that doesn't mean it won't happen at some point. Regardless, it's worth monitoring where Davis lines up against Denver because it seems increasingly likely that the 49ers want to get him back in the mix with the first unit in some capacity.

4. Working the slot: Last week's game against the Texans allowed for more than one Davis to have a successful first preseason outing. Cornerback Chris Davis was a surprise starter of sorts at nickelback and went on to perform well in that role. He was sticky in coverage, solid as a tackler and had a pass breakup. Niners coaches have said they would like to see different combinations in the secondary, so it's possible they'll re-work some things (possibly moving Jimmie Ward into the slot and having someone else move outside) or allow someone else to get reps as the nickel back. But if Davis can put together another strong effort, he'll bolster his case to become the starting nickelback.

5. Turnover turnaround: Kelly's biggest complaint coming out of the game against Houston was the fact that the offense had two turnovers, both fumbles. One came on a protection issue that led to Hyde coughing it up, and the other came inside Houston's 5 to kill a scoring drive. On the other side of the ball, the Texans fumbled twice but the Niners failed to recover both times, leaving them minus-two in turnover margin. That's not going to win many games regardless of who you are but with the Niners' tempo, sudden changes can be especially tough on a defense that is going to be on the field a lot anyway. Look for ball security to be a priority for the 49ers against Denver.