Adam Schefter of ESPN reported the news, noting that Seahawks head coach Pete Carroll said the injury was "a pretty severe situation right now." Earlier, Bob Condotta of the Seattle Times reported the injury "caused a lot of swelling and has a compartment element to it that has to be looked at immediately."
The 27-year-old finished with three catches for 26 yards.
His play this year has been a continuation of his breakout 2018 campaign, which saw him record 57 catches, 965 receiving yards and 10 touchdowns. These were all personal bests, and only five players in the NFL had more receiving yards.
While Lockett was named first-team All-Pro as a rookie due to his return ability, he seemed to put it all together as a receiver last year.
Lockett also finally seemed fully healthy after a leg injury at the end of 2016 appeared to hold him back throughout 2017. It seems his string of good luck has run out with the latest injury, however.
His absence could force rookie DK Metcalf into a bigger role in the offense, while Josh Gordon should also see more targets come his way.