The quarterback missed practices on Wednesday and Friday. Tannehill was listed as limited on Thursday.
Vrabel noted the team would wait as long as necessary before making a firm decision on Tannehill's availability.
The signal-caller injured his ankle in the Titans' Week 7 victory over the Indianapolis Colts. Tannehill missed one snap and returned to the game with a heavily taped ankle. On Friday, the Titans QB was listed with an illness, as well.
If Tannehill can't play in Week 8, rookie Malik Willis would be in line to make his first start. Willis appeared in mop-up duty in Week 2, completing 1 of 4 passes in the blowout loss to Buffalo. The rookie has taken most of the reps in practice this week with Tannehill injured.
Regardless of who is under center, expect the Titans to saddle up Derrick Henry for a large workload against a Texans defense that has been gashed on the ground this season, ranking last in the NFL against the run.