The Miami Dolphins may end up being without both of their starting offensive tackles for their Week 13 road matchup against the San Francisco 49ers. The Dolphins released their final injury report for Week 13 on Friday, and they officially ruled out right tackle Austin Jackson, while Terron Armstead is listed as doubtful.

Armstead and Jackson each came away from the Week 12 home win over the Houston Texans with an injury.

On Armstead’s part, he suffered a pectoral injury during the first half of the victory over Houston. He was then kept out for the second half, as Dolphins head coach Mike McDaniel called on Brandon Shell to fill in for him at the left tackle position.

The NFL Network’s Tom Pelissero noted on Monday that Armstead came away from the game with a Grade 2 pec strain.

During a press conference on Monday, McDaniel downplayed concerns that Armstead sustained a season-ending ailment in Week 12, as he made clear that he is “confident” that the veteran offensive lineman will once again suit up for Miami later this year.

After being sidelined from practice on Wednesday and Thursday, Armstead did make a return to practice on Friday, where he was a limited participant on the day.

On the other hand, Jackson’s injury-marred campaign continued in Week 12, as he left the game due to an ankle injury. While he did not reaggravate the nagging ankle ailment that he nursed for much of the first half of the season, Miami still elected to rule him out against the 49ers.

The Dolphins are now slated to call on Shell and Greg Little to start against the current NFC West leaders, although it remains to be seen exactly who will take the left tackle and the right tackle roles for the matchup. Nonetheless, Dolphins offensive coordinator Frank Smith is quite confident in the two heading into Week 13.

“I think both have shown flexibility, especially this season,” Smith said during a press conference on Thursday. “Both have played obviously on either side.

“With Brandon having to come in and jump in on the left in the course of that game, obviously when you’re going from the right side for several weeks and going back to left, it’s never as easy as everyone thinks it is. … Greg naturally was more of a left tackle. But both of them have shown the flexibility to do both, which has made it invaluable for us because beyond the starting five, you really have to look at being flexible to do whatever the needs of the day are.”

Miami has its sights set on picking up a crucial victory over San Francisco to extend its winning streak to six games.