ASHBURN, Va. -- Redskins wide receiver DeSean Jackson could miss 3 to 4 weeks with a strained left hamstring, coach Jay Gruden said on Monday.
"Possibly, it could be shorter, but you just never know with hamstrings," Gruden said.
Jackson was injured on the first play of Washington's second possession in a 17-10 defeat against Miami on Sunday. He was trying to catch Kirk Cousins' deep throw to the right sideline.
The three-time Pro Bowler led the Redskins with 1,169 yards receiving and six touchdown catches in 2014, his first season in Washington. His 20.9 yards per reception were tops in the NFL.
"You hate to lose a star, especially with his speed," Gruden said. "We feel good about the receivers that take his place, but nobody can substitute him for that burning speed that gets down field and scares safeties and corners to death."
A shoulder issue kept Jackson from playing in any games this preseason, but Gruden said it's unclear if that contributed to the receiver's current injury.
"He was still able to do a lot of running in that time," Gruden said. "So I don't think it really did. I think it was one of those things that happens to a wide receiver."
Gruden also confirmed that Washington had released kicker Kai Forbath and signed kicker Dustin Hopkins in an attempt to improve the team's kickoffs.
Also safety Duke Ihenacho will need surgery to repair a fractured and dislocated left wrist.
Forbath made 87 percent of his field goal attempts (60 for 69) in three-plus seasons for Washington. But he only had 18 touchbacks last season, which was 31st in the NFL.
Gruden disagreed that Forbath's release was directly related to Sunday's loss, in which he made a 45-yard field goal and missed a 46-yard attempt.
"We're not making Kai a scapegoat," Gruden said. "That's insane. What we're trying to do is improve our kickoff cover team and we're trying a young kicker who worked out here extremely well today."
Hopkins missed his 2013 rookie season in Buffalo with a groin injury. He was cut by New Orleans earlier this month, and has yet to play in an NFL game.
In other moves, the Redskins re-signed defensive end Frank Kearse after releasing him last week, waived linebacker Houston Bates and announced a one-game suspension for cornerback Chris Culliver for a violation of the NFL's personal-conduct policy.