EL SEGUNDO, Calif. — The Los Angeles Chargers held their 12th practice of training camp Tuesday at The Bolt, and now the team’s focus turns to the preseason opener at the Houston Texans on Thursday night.“I just can’t wait to watch them compete,” coach Jim Harbaugh said Tuesday before practice. “It’s that feeling in a game that is exciting for everybody in the entire organization.”The Chargers still have plenty to sort through with their roster as they are now more than halfway through camp. There is a starting job up for grabs along the offensive line. The backup quarterback position behind Justin Herbert feels unsettled. Young players in multiple defensive position groups have shown up in camp practices, creating some potentially difficult 53-man decisions.Here are the five areas of the roster I will be monitoring when the Chargers play real football for the first time this season Thursday night.A clearer picture at LGThe Chargers have defined starters at four spots on the offensive line. Rashawn Slater has not practiced in four days after suffering a minor flare-up last week in his surgically repaired left knee. He described the issue as “nothing to be concerned about” and said the missed time is more related to being “smart” and “thoughtful” as he works back from a torn patellar tendon.Slater is the starter at left tackle. Joe Alt at right tackle. Cole Strange at right guard. Tyler Biadasz at center. The open position is at left guard. Harbaugh said multiple players will get “opportunities” in the preseason opener, including veteran Kayode Awosika and rookie Jake Slaughter.Second-year offensive lineman Branson Taylor has also been in the mix at left guard with the starting group during camp. Trey Pipkins III was initially rotating in at left guard, though he has been playing tackle while Slater has been sitting out. Trevor Penning seems to have fallen out of this competition. On Tuesday, he worked at both guard spots, primarily with the third-team offense.When asked about the left guard competition Tuesday, Harbaugh specifically mentioned Slaughter, whom the Chargers drafted in the second round in April.“Jake Slaughter had a great weekend,” Harbaugh said. “If we were right up to the minute right now, yeah, really liked the tape from the weekend. And his confidence, it’s like he’s getting it. So that’s super encouraging.”Slaughter has looked capable when moving laterally in the run game. On Tuesday, he also gave up a pressure to edge rusher Bud Dupree in pass protection. He lost badly on a run-game rep against interior defensive lineman Jamaree Caldwell.Slaughter, Awosika and Taylor all got chances with the first-team offense Tuesday. Awosika gave up back-to-back sacks on his first two 11-on-11 reps with the starters but looked better in one-on-one drills. He had one of the best reps of the period, locking up interior defensive lineman TeRah Edwards.If Slaughter plays well Thursday night, he could become the leader in this battle.Mike McDaniel's new offense and more takeaways from Chargers training campRobert MaysIs a competition really shaping up for backup QB?Trey Lance was Herbert’s backup last season, and he entered camp in that role. But DJ Uiagalelei, who spent 2025 on the Chargers’ practice squad, has flashed at points during camp. He has shown more as a thrower than Lance, whose best attribute is his running ability.Lance’s skills come alive in a live-game environment because of the plays he can create with his legs. Thursday night should be an interesting test. Harbaugh said each quarterback will play a half.“Both have really acquitted themselves well, and the next piece is in the games and how they play,” Harbaugh said. “That’s something we’ll all see. I imagine, from what I’ve seen in practice, it’s going to be pretty close. They’re both good.”If Uiagalelei outplays Lance, we will have a true competition on our hands. Uiagalelei still puts the ball in harm’s way too often. He threw two more interceptions in Tuesday’s practice, one to safety Devin Grant and one to cornerback Donte Jackson. Harbaugh is pretty clearly leaving the door open, though.Fight for roster spots at back of CB roomFour cornerbacks feel like locks for the 53-man roster. Jackson, Cam Hart and Tarheeb Still have all rotated in with the first team. Still is working through an injury and did not practice Tuesday. Deane Leonard is the Chargers’ best gunner and should make the roster because of his special teams capabilities.Beyond those four, the competition is fierce. Nikko Reed and Eric Rogers made the 53-man roster last year as undrafted rookies. This year, undrafted rookies Avery Smith and Rodney Shelley have displayed playmaking through the first 12 practices of camp. The Chargers could keep five corners. They could keep six. They could even keep seven, as they did last season. Though Rogers was placed on injured reserve almost immediately after cutdown day, he missed the entire season.It is shaping up as four players battling for one or two spots. Last year, Reed and Rogers were two of the Chargers’ best preseason performers. They earned their way onto the roster. Can Smith and/or Shelley make a similar push? The depth in this room is still very much to be decided.Deane Leonard, left, who plays a big role on the special teams unit run by Chris Gould, center, should have a roster spot locked up. But Nikko Reed, right, is firmly in a battle. (Kirby Lee / Imagn Images)Can someone make a case as the fifth edge rusher?Khalil Mack, Tuli Tuipulotu, Akheem Mesidor and Bud Dupree are the top four edge rushers on the depth chart. The big question to answer through the preseason and the remainder of training camp: Will the Chargers keep a fifth?The two contenders are Kyle Kennard and Nadame Tucker. Kennard was a fourth-round pick in 2025. Tucker is an undrafted rookie. Kennard has looked decidedly improved in his second season. He was a non-factor as a rookie, only playing in five games. Through 12 camp practices this year, some of the pass-rush impact Kennard showed in college is starting to show up in the pros. On Tuesday, for instance, he won two one-on-one reps with two different moves. The first was a swim to the inside. The second was a chop to the inside.Tucker, meanwhile, has already displayed NFL power in team drills and one-on-ones. He beat Taylor with a bull rush in one-on-ones on Tuesday. He also overwhelmed Pipkins with a power rush, knocking the tackle off balance several yards into the backfield.The Chargers could end up keeping four edge rushers, but Kennard and Tucker are putting themselves firmly in the mix. They have to show up Thursday night to keep making their cases.