DAVIE, Fla. -- The Miami Dolphins did not activate practice squad quarterback Reid Sinnett to the 53-man roster Saturday, meaning Tua Tagovailoa is expected to be active and eligible to play Sunday against the Cincinnati Bengals.

Tagovailoa has been limited in practice with a left thumb injury for two weeks. The Dolphins haven't officially announced a starting quarterback for Sunday's game. Veteran Ryan Fitzpatrick is also on the active roster.

If Tagovailoa does indeed start, he will have some key help in the backfield as running back Myles Gaskin was activated to the 53-man roster Saturday. Gaskin is expected to return to the starting lineup Sunday after missing the past four games with a knee sprain.

Sinnett served as Fitzpatrick's backup in Sunday's 20-3 win over the New York Jets.

Dolphins coach Brian Flores has been clear that Tagovailoa is the starter when he's healthy.

"If he's healthy, he's the guy," Flores said after last Sunday's game "I don't know how many different ways we have to continue to say that."

Flores also said Tagovailoa was "very close" to playing last Sunday, and he has shown some improvement this week.

If Tagovailoa starts, it will be his first action since being benched in the fourth quarter of the Dolphins' 20-13 loss to the Denver Broncos -- his lone loss as a starter after winning his first three games. After Sunday's game against the Bengals, the Dolphins' schedule features four straight games against AFC teams in playoff contention.

Tagovailoa has been wearing a black spica splint in practice to provide support to the base of his thumb while allowing mobility to the rest of the fingers. He said earlier this week that he's "feeling good" and wants to play, but he deferred to Flores and the training staff.

Closer look at Tua Tagovailoa's left thumb during practice this week. (H/T @CTJPhoto) pic.twitter.com/EmmcCXzGCh

— Cameron Wolfe (@CameronWolfe) December 4, 2020

The Dolphins have been somewhat vague on their quarterback situation over the past two weeks. Tagovailoa and Fitzpatrick have both taken snaps, with little public indication of which way Flores has been leaning.

Tagovailoa suffered the injury after hitting a teammate's helmet while following through on a pass attempt in practice Nov. 25. Tagovailoa has participated in every practice since in a limited capacity.

As for Gaskin, his return comes at the perfect time as the Dolphins backfield has been struck hard with injuries. Running backs Salvon Ahmed (shoulder) and DeAndre Washington (hamstring) are doubtful to play Sunday, and Matt Breida was placed on the reserve/COVID-19 list Friday after missing practice with an illness. Safety Nate Holley was elevated as a replacement.

If Ahmed, Washington and Breida are all out, as expected, Gaskin and Patrick Laird would be the only healthy tailbacks. The Dolphins also have fullback Chandler Cox and receiver Lynn Bowden Jr. with some experience carrying the football, if needed.

Gaskin is still the team's leading rusher (387 yards). He had more than 20 touches in each of his past three games before the knee injury.