SANTA CLARA, Calif. — It’s a position that lines up mere feet from the quarterback. It’s one that’s been conspicuous in the San Francisco 49ers’ biggest moments under Kyle Shanahan. And, heading into Thursday’s preseason finale, it’s not resolved.In fact, you could argue the team is further away from a solution at left guard today, two days after training camp ended and six days before the 49ers board a flight to Australia, than it was when the summer session began a month ago.The most experienced candidate, Robert Jones, is out with a calf injury, although Shanahan is optimistic Jones will be back at practice next week. Another, Brett Toth, has been dealing with a concussion since early August. And Connor Colby, who seemed comfortably in the lead at the start of training camp, has largely been relegated to the second-team unit in recent weeks. Even Austen Pleasants, who drew more snaps at left guard in recent weeks, is now battling a knee injury.That’s left Carver Willis, a fourth-round rookie, taking the lion’s share of the first-team repetitions over the past two weeks. Willis is in line to start his second straight preseason game today in Las Vegas.49ers' talented running backs finally assembleMatt BarrowsAll the snaps Willis has been getting lately underscore two things:First, he badly needs them. He played tackle exclusively in college at Washington, and converting to guard in Shanahan’s system is not easy. Colton McKivitz, who was also a college tackle, tried it when he was a rookie in 2020 and was cut the following season. When he returned to the team, it was at tackle, his position ever since.“It’s extremely hard,” McKivitz said. “I went through it as a rookie, and it didn’t work out for me.”All the repetitions Willis is getting this close to the season, however, also show how much the 49ers believe in him. His first 11-on-11 snap with the first-string offense two weeks ago was rough. He gave up a sack to defensive tackle Osa Odighizuwa and allowed a second one later in that practice.