The Dallas Cowboys are now into their third week of training camp and it's time to take a look at some updates for the most important starting and backup competitions on the team.This week, we're going over what's going on with the starting jobs at left tackle, cornerback and linebacker. Two of those spots have clear favorites, while one of them is beginning to see a shift.We are also keeping tabs on key backup competitions at quarterback, running back and wide receiver to see who is emerging there with about a month left to go before Week 1.Let's get to it.Left tackleDallas Cowboys offensive tackle Tyler Guyton. | IMAGN IMAGES via Reuters ConnectThe left tackle competition that never even got off the ground looks to be all but over after head coach Brian Schottenheimer revealed the team would be keeping Tyler Guyton with the first team instead of rotating in Nate Thomas.Schottenheimer did not officially declare Guyton the starter but noted Thomas has to show the team a lot more before it can give him a real opportunity to compete for the starting job.The writing was on the wall even before Schottenheimer made the announcement, as Guyton had dominated first-team reps during the spring and through the start of training camp.LinebackerDallas Cowboys linebacker Jaishawn Barham. | IMAGN IMAGES via Reuters ConnectDee Winters entered camp as the favorite to start alongside DeMarvion Overshown, and while that remains the case, the gap has tightened thanks to a standout showing from Jaishawn Barham.However, Barham recently suffered a groin injury, and while it is not believed to be serious, missed time will halt the rookie's momentum toward pulling off an upset.CornerbackDallas Cowboys cornerback Cobie Durant. | IMAGN IMAGES via Reuters ConnectWith DaRon Bland seemingly locked into one side, Dallas has to figure out who will start opposite him.Shavon Revel and Cobie Durant are fighting for that spot, and right now it appears Durant is in the lead, according to Calvin Watkins of the Dallas Morning News, which isn't surprising because Durant continues to shine on a daily basis at camp.While unfortunate for Revel, he is also having a strong camp and that is great news for the Cowboys, as they'll have options if someone falters in 2026.Backup competitionsDallas Cowboys quarterbacks Dak Prescott (4), Joe Milton (10) and Sam Howell (16). | IMAGN IMAGES via Reuters ConnectQB2: Jon Machota of The Athletic said that Sam Howell is "clearly ahead of Joe Milton right now" in the race for QB2. That puts Milton firmly in danger of missing the cut later this month.RB2: Jaydon Blue and Phil Mafah are, at the very least, giving Malik Davis a run for his money, but Blue especially has been one of the bigger standouts at training camp. It's close, but Blue might have the edge for RB2 right now thanks to his explosive skill set and ability as a pass-catcher, an area in which Davis and Mafah are lacking.WR5: Calvin Watkins of the Dallas Morning News believes it'll be Jonathan Mingo securing the No. 5 wide receiver spot. He also doesn't think Dallas will carry six.Add us as a preferred source on GoogleFollow