LANDOVER, Md. -- The Baltimore Ravens won their 20th straight preseason game Saturday night, but running back J.K. Dobbins' knee injury loomed over any unofficial NFL record.

Dobbins was ruled out for the rest of the Ravens' 37-3 rout of Washington after suffering a left knee injury on the opening drive.

Ravens coach John Harbaugh declined to specify his level of concern about Dobbins' injury after the game.

"He'll get tested [Sunday]," Harbaugh said. "We'll see where we're at, at that point in time."

Dobbins lay on the ground clutching his left knee after being tackled on a screen pass on the ninth play of the game. He was sandwiched on the play, and his left knee took a direct hit from the shoulder of Washington cornerback Jimmy Moreland.

Dobbins needed help to get to the sideline and had his arms draped on the shoulders of trainers because he couldn't put any weight on his left leg. He was soon carted off to the locker room.

Ravens wide receiver James Proche let out a long sigh when asked about seeing Dobbins leave the field that way.

"That one hurts, bro, because you know how much work he put in [and] the type of guy he is," Proche said. "He loves the game. Any time a game is taken away from a dude like, you really feel for him."

Ravens quarterback Lamar Jackson said "hopefully" Dobbins doesn't miss time from the injury.

"That's a tremendous back," Jackson said. "But we have Gus [Edwards] and we have Ty [Williams]. Hopefully, he's good."

A second-round pick from a year ago, Dobbins was entering his first season as Baltimore's featured back. Last season, Dobbins was pivotal in the Ravens' late-season push to reach the playoffs, gaining 425 yards (eighth most in the NFL) and scoring six touchdowns in the final five regular-season games.

Last year, Dobbins averaged 6.0 yards per carry, the second-highest average by a rookie running back over the past 20 seasons, according to ESPN Stats & Information research. Only the Saints' Alvin Kamara (6.1) had a higher average as a rookie.

"I was hoping for nothing, but I know he's going to be fine regardless of what happens," Ravens linebacker Patrick Queen said of Dobbins' injury. "Prayers out for him, for sure."

Baltimore's is among the top backup running backs in the NFL. He was signed to a two-year, $10 million extension this offseason after being one of two players in NFL history to produce at least 700 yards rushing and average 5-plus yards per carry in the first three seasons of a career, according to research by the Elias Sports Bureau. The other is two-time Pro Bowl back Nick Chubb of the Cleveland Browns.

After Dobbins' injury, the Ravens rolled to wrap up their sixth straight perfect preseason behind Tyler Huntley's five touchdowns (four passing and one rushing). Baltimore eclipsed the Vince Lombardi-coached Green Bay Packers, who won 19 preseason games in a row from 1959 to 1962.

Although the official record is unknown, the Ravens' 20-game preseason win streak is the longest by anyone confirmed by Elias Sports Bureau since 1995.

The Ravens' last preseason loss was Sept. 3, 2015.

"I just think it's really cool. ... There's a lot of guys watching on TV telling their kids about that accomplishment and that they were a part of that," Harbaugh said of the preseason record. "That's the most meaningful thing."