Long left practice Monday after hurting his right knee when he went down in a pile on a pass play. An MRI exam showed the injury wasn't serious, said a person familiar with the diagnosis, who spoke to the Associated Press on condition of anonymity because the Dolphins didn't comment on the injury.
Back trouble slowed Long last season, and he went on injured reserve before the final game because of a torn right biceps. He nonetheless was chosen a Pro Bowl starter at left tackle for the third consecutive year.
Although Long has missed only two games in four NFL seasons, he has dealt with knee trouble in the past and wore a brace on his right knee Monday. Any absence would be especially worrisome with rookie Ryan Tannehill preparing to make his first NFL start in the season opener Sept. 9.
"It's a tough situation any time one of your teammates goes down," Tannehill said. "Hopefully it's not too bad and we can get him back soon."
Rookie Jonathan Martin, who protected Andrew Luck's left side at Stanford, moved over from right tackle to fill in for Long.
"I'm pretty comfortable on that side," Martin said. "Wherever they need me, I'm ready to go. I know the offense pretty well. I just had to flip things around in my head a little bit. I played that position for eight years in high school and college, so I'm pretty good at it."
Artis Hicks joined the starters at right tackle.
The Dolphins will play their final exhibition game Wednesday at Dallas.