Rookie Jonathan Martin moved from right tackle to the left side to replace Long against the Patriots, and if he plays well in the final four games, the switch could become permanent.
Long, a perennial Pro Bowl tackle since being taken with the No. 1 overall pick in the 2008 draft, earns a base salary of $11.2 million this season. He would receive $15.4 million next year if the Dolphins give him a franchise tag. That's likely more than Miami will be willing to spend, given that Long has battled injuries for much of his career and has endured a disappointing season.
The Dolphins (5-7) have lost four of their past five games, and their already slim playoff hopes might be quashed Sunday, when they play at NFC West leader San Francisco. So the timing's right to start thinking about next year.
Aside from addressing the situation at left tackle, upgrading the offense will be the priority, and the 23-16 loss to New England reinforced that notion. The Dolphins are averaging 18.9 points per game, sixth worst in the NFL.
''It's hard to win a lot of games scoring that many points,'' coach Joe Philbin said Monday. ''It probably would stand true in high school football.''
And now the Dolphins are prepared to move forward without their star offensive lineman.
'If that's the case, we'll go to work and get five guys ready to go up front,'' Philbin said. ''He has been an excellent leader. He's a valued member of the offense. However, injuries occur with every team. Ours is no different.''
Martin, a second-round draft pick, protected Andrew Luck's blind side as a left tackle at Stanford. He has started every game this year at right tackle, and Philbin said the rookie fared well after Long went out.
''He did a good job. He played well,'' Philbin said. ''He has a bunch of reps in his history from college playing over there. Here he doesn't get a lot of repetitions over there, but I thought he made a good adjustment in the middle of the game.''
Nate Garner, who has nine career starts, took over at right tackle.
Long has missed only two games in five NFL seasons. He was chosen a Pro Bowl starter each of the past three years and was a front-runner to be selected this year.
''He has been a good player for a long time, and he's the leader on the offense,'' quarterback Ryan Tannehill said. ''So it's tough to replace him.''
Even so, Long has become a less dominant blocker as his injuries accumulate. He was slowed by an ankle injury as a rookie and hurt his shoulder in 2010. Last year he battled back trouble, then missed the final game with a torn right biceps. He missed practice time this season because of a right knee injury.
Revamping the line would present yet another challenge for an offense that has sputtered. Tannehill ranks 31st in the 32-team league in passer rating, and Miami ranks 21st at 3.9 yards rushing per attempt.
A little more production might make a big difference, because five of the seven losses have been by a touchdown or less.
Against New England, the Dolphins totaled only 277 yards. Tannehill went 13 for 29, the third time he has finished below 50 percent, and twice missed an open Brian Hartline deep.
''You can't play the coulda-woulda-shoulda game,'' Hartline said. ''But they were big plays, and to beat a team like that, you have to make those kind of plays.''