The San Francisco 49ers preseason opener was a good chance for some players to lock down starting spots. However, other players are starting to see their chances slip away this summer. Who are the players losing their ground?6 San Francisco 49ers in Danger of Losing Their JobsChristian Kirk It is unfortunate that Kirk got hurt, but he has opened the door for other names to step up. Demarcus Robinson has been great in training camp and did not even play in the preseason. Rookie De’Zhaun Stribling was excellent in the preseason and made a push to jump Kirk. Even second-year receiver Jordan Watkins flashed and locked down a punt return job. With these three being added to Mike Evans and Deebo Samuel, there are five receivers ahead of Kirk.IMAGN IMAGES via Reuters ConnectConnor Colby Colby entered training camp as the most likely Week 1 starter at left guard. After one preseason game, he is the third most likely. San Francisco played Robert Jones over him at left guard, and he looked good. Even rookie Carver Willis played the second half at left guard. Colby spent the entire night at right guard. It is hard to win a starting spot when you do not play that position.Nick Martin The same can be said for Martin. Reports were that he was getting work next to Dre Greenlaw and Fred Warner with the starters. However, with those two out, the team leaned into Garrett Wallow and Jaden Dugger. Martin played after the rookie fifth-round pick and played into the second half. He also missed a tackle. He is a third-round pick entering his second season, but the team is running out of reasons to keep him. Nate Hobbs and Jack JonesThese two were signed to push Renardo Green and make the seat warm for Upton Stout. However, Green and Stout sat out the preseason opener with the starters. Jones got hurt in the game, and Hobbs did not play due to injury. He will miss a few weeks. These two are not starting.Adrian MartinezIt should be no surprise, but Martinez officially lost the number three spot to Kurtis Rourke, assuming he is healthy.Bryson Eason Eason has been competing with Sebastian Valdez and James Thompson for the fifth interior defensive line spot. Valdez started next to Alfred Collins, and Thompson flashed throughout the night. Now, the practice squad might be out of the picture for Eason. Add us as a preferred source on GoogleFollow