Tannehill practiced on a limited basis on Wednesday, but did not attempt any passes.
"He just can't throw at this time," Gase said, according to the Miami Herald.
Gase believes Tannehill will return at some point in the 2018 season and did not rule out Tannehill playing against the Houston Texans in the next game.
But on Sunday it will be Osweiler, who completed 28-of-44 passes for 380 yards, three touchdowns and two interceptions in the overtime win over the Chicago Bears last week. He rallied the Dolphins from a 21-10, third-quarter deficit.
"He did a good job of not panicking when we were down," Gase said of Osweiler. "He had a couple of interceptions, but he did a good job of moving on to the next series."
Osweiler's chief target will be wide receiver Albert Wilson, who had 136 of his 155 receiving yards after the catch in last week's win over the Bears. He leads the NFL with 324 yards after the catch this season.
The Dolphins, who are 4-2 and are tied with the New England Patriots for the top spot in the AFC East, will be going up against a Lions defense that has given up an average of 27.4 points per game, which ranks 25th in the NFL.
The Lions rank seventh in the league against the pass, but they are 30th against the run, giving up 145.8 yards per game and 5.3 yards per carry.
That may open things up for Dolphins running backs Frank Gore and Kenyan Drake. The 35-year-old Gore is coming off a 101-yard game against the Bears, and he'll have the added incentive this week of playing against a Lions team that brought him in for a free-agent visit this offseason but decided to sign LeGarrette Blount instead.
The Lions (2-3) are coming off a bye, but they beat the Green Bay Packers 31-23 the week before. Detroit quarterback Matthew Stafford had an efficient game against the Packers, completing 14-of-26 passes for 183 yards, two touchdowns and no interceptions.
In fact, Stafford has been effective in all four games since his awful showing in the season opener, when he threw four interceptions in a 48-17 loss to the New York Jets. Since then, he has thrown nine touchdown passes with just one interception.
Stafford's play has paralleled the Lions' improvement in short-yardage situations. They have converted all five of their third- or fourth-and-1 running plays through the season's first five games.
"That's an important situation in these close games, in these tight games," Lions offensive coordinator Jim Bob Cooter said. "One that our guys are doing a nice job of executing their role, executing their job each week. That's been a productive thing for our offense, keeping us on the field, creating first downs and sort of keeping us out there to keep going. It's been a positive."
Rookie Kerryon Johnson has emerged as the Lions' No. 1 running back, although Blount has been the key performer in red-zone and short-yardage situations.
The 250-pound Blount has converted five of six rushes with one yard to go. He was stopped for no gain on a second-and-1 play against the Packers, but then gained six yards on the next snap. He has also scored a pair of touchdowns on 1-yard runs.
Those short-yardage situations make his 2.5 yards per carry average look worse than it should.
This week, the Lions face a Dolphins defense that has been effective in the red zone and has stopped six of 11 third- or fourth-and-1 runs.
"We need to keep improving, keep working on it, keep it a positive as we go forward," Cooter said. "There'll be ups and downs as we go through the year, different challenges every defense sort of makes you face. So we'll keep working on it, keep working to improve and we'll try to keep things headed in the right direction."
Lions guard T.J. Lang is on track to return to action after missing the game against the Packers with the sixth documented concussion of his career.
Detroit defensive end Ziggy Ansah might return to action Sunday after missing the Lions' last four games with a shoulder injury. He had 12 sacks last year.
A Dolphins win on Sunday would give them their first 5-2 start since 2003 and their first 4-0 home start since 2000.