Colin Kaepernick limited in Niners practice after sitting out Thursday

SANTA CLARA, Calif. -- All week, San Francisco 49ers coach Chip Kelly has refused to name a starting quarterback for his team's preseason opener against the Houston Texans on Sunday.

By way of explanation, Kelly cited concern that Colin Kaepernick or Blaine Gabbert could suffer an injury and not be available or be limited for the game.

While Kelly often made reference to someone "turning an ankle," shoulder fatigue might have been a better guess. Kaepernick did not throw in practice for the second consecutive day Friday because of what he called tightness in his right (throwing) shoulder. Gabbert took all of the repetitions with the first team instead of the customary 50-50 split with Kaepernick.

Kaepernick told reporters after Friday's joint practice with the Texans that he thinks he'll be able to play Sunday, but his status will be evaluated as the game nears.

"His throwing shoulder's, just from the accumulation of what we've been doing, is a little sore," Kelly said. "So we're going to monitor that. Hopefully we can get him to play on Sunday.

"We said that all along, to determine what's going to go on Sunday won't be determined until after we come out of here today. ... So, we're going to keep a good eye on him today."

Kaepernick wasn't completely out of the mix in Friday's practice, but Kelly's definition of limited meant he stuck with handoffs and simulated reps standing behind the quarterback. That's similar to what Kaepernick did in the spring when he was recovering from shoulder, thumb and knee surgeries.

In fact, it was the leftover effect of that shoulder surgery that has Kaepernick feeling the tightness.

Kaepernick said he threw over the summer but that there's no way to replicate the different arm action required in live reps during practice. Kelly said his quarterbacks throw the ball between 86 and 102 times during a normal practice session.

As a former high school baseball pitcher, Kaepernick said his arm usually "snapped back" quick after similar arm fatigue.

"I think it's been the buildup [of reps]," Kaepernick said. "You don't really get the reps of live action and that violent motion when you are practicing in the offseason. So I think it's just building my endurance in that area."

On Tuesday, Kaepernick stopped in the middle of practice to have his arm stretched by one of the team trainers. He finished the practice and participated in Wednesday's workout at Kezar Stadium, a practice in which he struggled.

Kaepernick then didn't practice for what Kelly called a planned day off Thursday and was again limited Friday.

"That's why we had planned on actually taking yesterday off," Kelly said. "We knew that going in. He didn't throw during the spring full because of coming off of [the injury]. So, it's just trying to get his arm back to where we can just use him every day. If we've got to take a day off in between, it's not a real big deal."

Whether Kaepernick plays, let alone starts, Sunday's game against the Texans remains unclear, but he did say he "most definitely" expects to start a game at some point in the preseason.

"I would have loved to got those reps, but it's also something that we are in preseason practice and we don't play a game for another month, so we want to make sure we stay ahead before we get to the season," Kaepernick said.

Gabbert, meanwhile, said he felt good during Friday's practice and directed an offense that had some success against Houston.

As for starting against the Texans, Gabbert said he isn't too worried about something that he doesn't control, even if signs point to him getting the first shot.

"It's up to Coach Kelly," Gabbert said. "Coach Kelly makes those decisions and when I do get the chance to get out there and play, I'm just going to make the most of my opportunity. That's all you can do. Whether you're going in the first, second, third or fourth quarter, every quarterback wants to go out there and compete, have fun and just execute our offense and move the ball down the field."