"We're probably in a lot better place than we were after the game," Tomlin said Tuesday. "... I can definitively say that T.J. won't play this week [against the Patriots], but I won't make any commitments beyond that.
"We're encouraged, and we'll just continue to look at the situation and gain opinions and do what's appropriate."
Asked to clarify if being encouraged suggests the Steelers don't believe Watt has a season-ending injury, Tomlin said: "That does suggest that, yes."
Watt on Tuesday tweeted a gif of Arnold Schwarzenegger's Terminator character saying, "I'll be back."
Watt appeared to suffer a torn left pectoral muscle in the final seconds of regulation when he tried to sack Bengals quarterback Joe Burrow, and as he walked off the field, he told medical personnel that he tore his pec.
Asked if Watt would go on injured reserve, Tomlin was noncommittal.
"We got time to make decisions such as that, IR decisions that have to be made by the end of the week relative to this game being a counter," Tomlin said. "... We're not in a hurry to gather information too quickly. We'll see how his body responds. We'll get second and third opinions. And at the end of the week, or at some point we'll do what's appropriate."
Injured reserve would rule Watt out for a minimum of four games. The Steelers can designate up to eight players to return from IR throughout the season and each player can return twice.
Watt's long-term availability likely hinges on whether or not he needs surgery. Tomlin wouldn't say Tuesday if surgery was ruled out.
In Watt's absence, the team will first turn to outside linebackers Malik Reed, acquired in a trade with the Broncos last month, and Jamir Jones, who the organization grabbed off waivers. The Steelers signed veteran linebacker Ryan Anderson to their practice squad later Tuesday, but Tomlin didn't commit to playing new faces on Sunday.
"I think maybe we've worked some people out already today in that vein, but whether or not it leads to participation remains to be seen," Tomlin said.
Tomlin was also encouraged by the prognosis of running back Najee Harris' lower-body injury. He said Tuesday that Harris did not aggravate the Lisfranc sprain on his left foot that sidelined him for most of training camp.
"Najee is really optimistic," Tomlin said. It's good to be young. He appears to be in position [to play], but he's going to have to practice and prove his readiness."