Romo missed Sunday's 34-14 loss to St. Louis with a broken little finger on his throwing hand. Brad Johnson started in place of Romo and was intercepted three times.
Phillips said Romo could have played against the Rams but program drills showed a lingering problem.
"We didn't feel like he'd be effective," said Phillips. "He was having trouble handling the football in the pregame warm-ups. Then we got into a situation where it wasn't prudent to put him in anyway.
"I think he's going to be similar to where he was last week."
Romo suffered the injury Oct. 12 during a Dallas overtime loss to the Arizona Cardinals. It was initially thought Romo would be sidelined for a month but he was throwing during practice last week with a protective splint on the injured finger.
In six games this season, Romo has completed 64 percent of his passes for 1,689 yards with 14 touchdowns and five interceptions.
Dallas (4-3) plays Tampa Bay (5-2) Sunday in Texas Stadium.