The San Francisco 49ers met Thursday night for their preseason opener at Levi's Stadium, and Kyle Shanahan's team was handed a 19-13 loss in the exhibition battle just days after they conducted a joint practice.Tennessee had most of their starters play two quarters, while San Francisco kept most of theirs on the bench for a game where the result doesn't really matter.With the loss, the 49ers had some players who didn't have the best night. Let's take a look at some of San Francisco's worst performers from Thursday night.LG competitionRobert Jones and Connor Colby have been battling to be the team's starting left guard in 2026, but it hasn't been great. On Thursday, Jones started on the left, and Colby started on the right. Neither should be happy with their performance while pass blocking or run blocking. San Francisco may want to seriously consider an upgrade at the position.RB Patrick Taylor Jr.None of San Francisco's running backs were overly impressive in this game, but Taylor was by far the worst. He finished with -5 yards on five carries with a long rush of one yard. While the broadcast mentioned that Taylor has a strong chance to make the roster, if he does, it will be because of his special teams work. DE Romello HeightHeight was San Francisco's top defensive pick in the 2026 NFL draft, as they took him with pick No. 70 overall in the third round. With other rookies flashing in this game, Height was mostly invisible in his limited snaps. The 49ers need pass rushers to step up this year, and this may have been his first opportunity in an NFL game, but it would've been nice to see him do something.Backup centersDrake Nugent and Doug Kramer Jr. filled in for Jake Brendel on Thursday, and they weren't overly impressive. In fact, there were multiple poor snaps. Some snaps were off target, resulting in fumbles or mistimed plays, while other snaps seemed to come before the quarterback expected the ball. That can't happen when the games actually matter.More 49ers: 49ers WR Ricky Pearsall reveals expected timeline for recoveryThis article originally appeared on Niners Wire: The worst parts of the 49ers preseason loss to the Titans