"We can't wait to watch him take the next step in this process," Tomlin said Monday, "which is play football."
Spence, a third-round draft pick in 2012, hasn't played since sustaining a career-threatening knee injury in the Steelers' final preseason game his rookie season. Linebackers coach Keith Butler said last year that it would be a "miracle" if Spence played again after he shredded several ligaments and suffered nerve damage in his knee.
But Spence is working out with his teammates in Pittsburgh's offseason program, and he is a candidate to contribute at a position where the Steelers could use an impact player.
"I'm not going to assume he's starting from ground zero," Tomlin said. "These haven't been empty days for him since he's been here in terms of the rehabilitation process and what's he's been able to do in terms of learning our system."
The Steelers drafted Spence with the hopes that the former Miami Hurricanes standout would become a long-term starter at inside linebacker. Tomlin said it is too early to tell how much Spence will be able to do on the field or whether he will be the player he was before the injury.
In other Steelers news:
• Offensive tackle Mike Adams received a vote of confidence from Tomlin and general manager Kevin Colbert on Monday. There had been speculation about Adams' standing since late last week, when three men were found not guilty of stabbing him last year after defense lawyers argued that Adams had been drunk and made up a story that his alleged assailants tried to carjack him. "I'll say one thing," Colbert said. "I'm just glad Mike Adams is a Steeler."
• Tomlin said the Steelers have not ruled out bringing back veteran defensive end Brett Keisel for one more season. The 12th-year veteran remains unsigned but the Steelers have been focusing on the draft, where they are expected to draft at least one defensive end prospect. "Obviously it's incomplete," he said of the defensive end position. "We've lost more than we've added. We'll rectify that."