"I thought we allowed (the Colts) to stay on the field some time with some shoddy tackling, especially early," Tomlin said. "And you give up big plays, you have a chance to lose football games."
Colts quarterback Jacoby Brissett threw 63- and 60-yard touchdown passes to help Indianapolis (3-7) take a 17-3 lead.
"You have to give those guys credit," Tomlin said. "They did a nice job of getting over the top of us. "We have to do a better job in third-down situations. We are fortunate to win this game. So, obviously we will get back to the lab and get to work."
--Brissett in concussion protocol
Colts quarterback Jacoby Brissett, who completed 14 of 22 passes for 222 yards and two touchdown passes, is in concussion protocol after a third-quarter tackle.
He was first evaluated by team doctors, which Brissett passed, and returned to the bench but was not permitted to return to the game.
When an independent neurologist was available, Brissett again passed the test and played the rest of the game.
After the game, Brissett returned to the locker room where he again developed symptoms and now is back in concussion protocol.
--Haden suffers broken leg
Pittsburgh cornerback Joe Haden suffered a broken left fibula during the first quarter and quickly left for the locker room.
--Colts struggle at home
With the loss to the Steelers, the Colts are now 2-3 at home this season.
Indianapolis has beaten winless Cleveland and San Francisco in Lucas Oil Stadium, but has lost to Arizona in overtime, Jacksonville and now the Steelers.
In the AFC South, the Colts trail Tennessee (6-3) and Jacksonville (6-3) by four games in the loss column.
The Colts are heading into their bye week and then host the Titans on Nov. 26.