The Washington Commanders got a ton of encouraging evaluation information from Friday night's 20-7 preseason win over the Miami Dolphins, but the team left Northwest Stadium with one lingering question about backup quarterback Marcus Mariota. With 26 players held out of the game, including starting QB Jayden Daniels, Mariota got the start but only lasted four plays before going down with an apparent leg injury. Mariota had just completed a 22-yard pass to Dyami Brown before going down on the following handoff to Kaytron Allen and eventually leaving for further evaluation. Mariota got hit pretty hard on the play to Brown, but stayed in the game until the handoff on the next play, when he appeared to grab at his knee. He was able to walk off the field on his own.Mariota enters the season as Washington’s established No. 2 quarterback behind Daniels, with two developmental prospects behind him who are far from NFL-ready; he is the last line of defense if something happens to Daniels. His health matters far more than the outcome of an August game. Commanders head coach Dan Quinn had no update on Mariota when asked after the game: "I don't. I know we're connecting on Sunday, so I'll give an update on Marcus and some of the other guys that we've talked about who couldn't be back." With Mariota leaving early, Sam Hartman came in sooner than expected. Hartman and rookie QB Athan Kaliakmanis handled the quarterback work the rest of the night. That is how thin the depth at quarterback is in the NFL, where one injury to your backup and you're down to developmental players still learning. Washington can feel good about plenty from its first preseason game, but Mariota’s status is the development that carries consequences beyond the roster evaluations taking place at the bottom of the depth chart.Washington's defense started the game looking nothing like the team that controlled things in Wednesday's joint practice session, as Miami drove 93 yards on 14 plays for the game’s opening touchdown. It should be noted that Washington rested most of its established contributors while Miami opened the game with many of its starters, including Malik Willis and De’Von Achane. After that opening drive, Washington never gave up another point despite Miami having seven more possessions.The defense forced three turnovers and repeatedly gave Washington shorter fields to contend with on offense. The night was a reminder of one of Daronte Jones’ major camp priorities — creating turnovers and making offenses pay when opportunities present themselves.