Carroll said the team hopes Dickson is back in four to five weeks. That timetable would mean his status for Seattle's Sept. 8 opener against Cincinnati is up in the air.
Quarterback Geno Smith, who's competing with Paxton Lynch to be Russell Wilson's sole backup, will start the Seahawks' preseason opener Thursday night against Denver, then will have an unspecified procedure, according to Carroll.
Carroll said he'll have more information postgame. The first indication that Smith is dealing with an injury came Tuesday, when he didn't practice. Carroll said Smith should be OK for Seattle's second preseason game, Aug. 18 at Minnesota.
"He's got an issue that we're dealing with that we're going to tend to after the game," Carroll said of Smith. "He's going to play in the game. He's going to start the game and get a chance to play some good football for us, but we're going to fix him up after that."
Wilson won't play Thursday, so Lynch will play extensively against the team that drafted him in the first round in 2016 and waived him after two disappointing seasons.
Wilson has played in every preseason opener since his rookie season in 2012. The only two preseason games he hasn't played in were the past two finales. He will be far from the only starter who won't play, Carroll indicated without specifying which ones will sit. He said the starters got nearly twice the work in Tuesday's practice as they normally would, in order to make up for the reps that some of them won't get Thursday.
"More than ever, we have a lot of guys that we need to play," he said. "We've got a big competition at the quarterback position in particular. We want those guys to play as much as they can and play their way into their spots. I don't want these to be decisions that we have to make without a lot of great information, so that's what's most important right now. We have a lot of competition at the receiver spot, we have a lot of competition in the offensive line. We're going to be able to play a lot of guys in the game and see how they can do."
Carroll said rookie defensive end L.J. Collier, who suffered a foot sprain on the fifth practice of training camp, has since seen an out-of-town doctor who gave him "a really good update that everything is in line." Carroll wouldn't venture a guess as to when Collier, Seattle's first-round pick, will be back.
"He's out of the boot, he's moving," Carroll said. "It should be a normal process now, bringing him back as he can handle and tolerate, so it would be ridiculous for me to make a guess on that one, but we're real encouraged. It's nothing beyond what we thought."
Rookie receiver DK Metcalf will play Thursday after missing the team's weekend scrimmage with an oblique injury, Carroll said. Not expected to play are: running backs C.J. Prosise (hip strain) and Travis Homer (quadriceps); tight ends Will Dissly and Jacob Hollister (groin); and safety Delano Hill. Dissly, who would likely start in Dickson's absence, is coming off a torn patellar tendon that cut his rookie season short. He is further along than the team expected, Carroll said, but is being held out Thursday as a precaution.