Garrett will then be re-evaluated, according to the team. High ankle sprains sometimes sideline players for four to six weeks.
"We are going to be week to week," Browns coach Hue Jackson said. "Let's see where we are week to week, and we will go from there."
"Obviously we would like to have him out there, but again, as I said several times before with not just his situation, these things happen in football," Jackson said. "Unfortunate. He is one of our better players, and we wish we had them all out there, but we will have him out there at some point in time soon. We will go from there."
Garrett, the top overall pick in the 2017 draft, was hurt Wednesday during Cleveland's first full practice leading to the opener. The injury occurred during a team drill when Garrett was engaged with an offensive lineman and a teammate fell against the side of his lower leg. Garrett left the field soon after.
"Oh yeah, somebody got thrown into the back of his leg by accident," Jackson said. "It wasn't intentional, and those things happen. It wasn't planned. Nobody tried to have it happen. He didn't try to have it happen. It is football. Those things happen sometimes when you are out there practicing. It was unfortunate that it happened, and we are going to move on from it."
Garrett's loss is another blow for the beleaguered Browns, who went 1-15 last season and have had their share of costly injuries in recent years. Quarterbacks Robert Griffin III and Josh McCown were hurt early last season. Wide receiver Corey Coleman, a first-round pick, missed six games with a broken hand, and Cleveland lost both starting guards to torn foot ligaments.
This is the second time the 6-foot-4, 275-pound Garrett has been hurt as a pro. He suffered a lateral sprain to his left foot during minicamp while pressuring former Browns quarterback Brock Osweiler. The injury was initially thought to be serious, but Garrett's foot was immobilized in a walking boot and he recovered in time for the start of training camp.
The Browns eased him into practices, but it wasn't long before Garrett was dazzling Cleveland's coaches and teammates with his speed and strength. Garrett also impressed with his work ethic, staying after practice to run wind sprints to build stamina.
Information from ESPN Browns reporter Pat McManamon and The Associated Press was used in this report.