The 29-year-old Texas A&M product suffered the knee injury during a practice in early August.
He was coming off a solid 2016 season in which he completed a career-best 67.1 percent of his passes for 2,995 yards with 19 touchdown passes and 12 interceptions across 13 games. His 93.5 passer rating also set a new career high.
Tannehill missed the final three contests of that year with a separate knee problem.
Last month, Gase called the quarterback's latest recovery "impressive" and noted Tannehill stayed around the team throughout the season despite being unable to play.
"Ryan, that's just him," he told reporters. "If I told him he wasn't allowed to be around, he'd still be around. He's never gonna be too far away. He wants to hear what we're doing. He knows how offenses go and evolve during the season and just wants to make sure that he's staying with us."
Tannehill was always expected to reclaim the starting job in 2018 barring a rehab setback.
Cutler, who entered a short-lived retirement and planned to transition to broadcasting with Fox Sports before signing with the Dolphins, only inked a one-year contract. Backup Matt Moore owns a mediocre 81.2 passer rating in 49 career appearances. He's also an impending free agent.
Tannehill is under contract through the 2020 season.