Until, suddenly, they weren't.
Now a promising start has quickly morphed into an early season crossroad.
Tampa Bay's Vincent Jackson's diving 5-yard touchdown grab with 7 seconds left lifted the Buccaneers to a stunning 27-24 win on Sunday.
The 6-foot-5 wide receiver laid out to haul in Mike Glennon's pass in the left corner of the end zone, sending their teammates spilling onto the field in celebration and the Steelers left wondering how they let a game that looked like a gimme on the schedule get away.
"We've got to cut out mistakes, that's what's beating us," Pittsburgh defensive end Brett Keisel said. "We can't go out and expect to beat an NFL team and beat ourselves as well."
The Steelers (2-2) began the day second in the NFL in penalties and only padded their ranking. Pittsburgh drew 13 flags for 125 yards, including a half-dozen personal fouls that sapped momentum and left the door open long enough for the resilient Buccaneers to slip through.
Pittsburgh coach Mike Tomlin called the steady stream of flags "inexcusable," ''unacceptable" and "ridiculous."
"We need to fix it," he said. "And if we don't, we'll continue to lose close football games."
Tampa Bay (1-3) lost to Atlanta 56-14 a week ago, but responded on the road to beat the Steelers and give Lovie Smith his first victory in his second head coaching stop.
Glennon passed for 302 yards in his first start of the season, including a 41-yard catch-and-run by Louis Murphy that set up Jackson's winning score.
"It's a long time coming," Smith said. "Last week we were embarrassed by our play."
This time, the embarrassment belonged to the guys on the other side of the field.
Ben Roethlisberger passed for 314 yards and three touchdowns, but Pittsburgh couldn't protect a seven-point lead in the fourth quarter. Antonio Brown caught seven passes for 131 yards and two scores, but let a long heave from Roethlisberger with 7 minutes to go glance off his hands.
"I should have brought down that catch on that flea-flicker play and maybe it would have been a difference in the outcome of the game," Brown said.
The teams combined for 22 penalties in an ugly game that featured little flow and plenty of missed opportunities, most of them by the Steelers.
Pittsburgh rallied from an early 10-point deficit and appeared to be in complete control at times, but they couldn't shake the Buccaneers.
Tampa Bay twice was down a touchdown in the second half. Both times the Buccaneers, who needed two late scores against the Falcons to avoid the worst loss in franchise history, came through on the road.
A 3-yard touchdown run by Doug Martin tied the game at 17 in the third quarter. After Roethlisberger found Heath Miller for a 5-yard touchdown to put Pittsburgh back in front, Tampa Bay kept coming against a Steelers defense that struggled to get to the quarterback even with the addition of linebacker James Harrison. The five-time Pro Bowler returned to Pittsburgh after an 18-day retirement to help an injury-depleted defense.
The 36-year-old played more than a dozen snaps yet couldn't find his way to Glennon, who was sacked just once.
"Just real inconsistent," Harrison said. "We're not playing up to the level we're capable of playing."
Not when it mattered anyway.
Patrick Murray kicked a 27-yard field goal to get the Buccaneers within 24-20 with 11:37 to go.
Twice Tampa Bay had the ball with a chance to take the lead. The first drive ended when Glennon overthrew Jackson in the back of the end zone on the first play after the two-minute warning.
Pittsburgh couldn't muster a first down after center Maurkice Pouncey drew a false start penalty, giving the Buccaneers one last shot.
Taking over at the Steelers 46, Glennon hit Murphy in stride. Murphy was finally pulled to the ground at the Pittsburgh 5. Jackson couldn't haul in a pass on second down, but responded on the next play by stretching out in the corner to cap a turnaround that saw the Buccaneers go from woeful to winners in all of 10 days.
It also put an emphatic stop to the brimming optimism in Pittsburgh. The Steelers were dominant in a victory at Carolina last Sunday. Given a chance to move to 3-1 for the first time since 2010, when it won the AFC championship, Pittsburgh is left searching for answers after another maddeningly erratic performance.
"Every game is critical right now," Steelers defensive end Cam Heyward said. "Even though it's early, these early games can affect you long term. We need to get rid of the mistakes."
NOTES: Steelers RB Le'Veon Bell, who came in leading the NFL in total yards, ran 19 times for 63 yards and caught six passes for 46 yards. ... Roethlisberger became the 12th player in NFL history to go over 35,000 yards passing with one team. ... Pittsburgh is at Jacksonville next week.