The G-Men gained a whopping 182 yards against the Steelers with Manning completing just over 40 percent of his passes.
Beyond Manning's poor performance, Big Blue's running game was a no-show, and the receivers struggled to get separation against one of the league's top pass defenses.
So, what should New York address at the ole drawing board this week?
Well, here are five keys to the Giants offense returning to form in time for next week's matchup against the Cincinnati Bengals.
Eli Manning, who looked so good during the Giants' four-game winning streak, had one of the worst games of his career Sunday.
Manning completed only 41 percent of his passes against the Steelers for a mere 125 yards; as a result, New York was just 2-for-10 on third-down conversions.
Manning never got in a rhythm Sunday, was under pressure throughout and could not spark the fourth-quarter comeback Giants fans have become accustomed to over the years.
With the Giants clinging to a 10-point lead, Manning looked undaunted, but also uninspired. He did little to change his strategy against a defense that was sticking his receivers off the line and collapsing his pocket with ease.
Manning, like the rest of the Giants, needs to forget about this game and come back rested and confident.
He has the "short memory" a star quarterback needs, so expect him to return to form against the Bengals.
The Giants offensive line, overmatched by the Steelers front seven, collapsed on Eli Manning and failed to forge sizable holes to help the running game.
Missed blocks, missed assignments and misreads were abundant as Pittsburgh gave the G-Men several different looks, keeping the line off balance all day.
Over the four-game win streak, especially the two huge games by Ahmad Bradshaw, the Giants' running game looked like it was here to stay.
But Sunday's 48-yard debacle may have set the team back light-years or at least to midseason 2011 when Big Blue could not run a personal ad without getting stuffed.
Of everything that went wrong on Sunday against Pittsburgh–and there was a lot–this is the one fix that may prove the most challenging.
Bradshaw has been inconsistent, Andre Brown was unimpressive and the rookie, David Wilson, was a nonfactor.
Eli Manning threw for 125 yards.
Not in a quarter. Not in a half. In an entire game.
That number speaks volumes about the whupping that Pittsburgh gave to Manning and the Giants receivers.
Other than Victor Cruz, the Giants receivers were invisible Sunday.
Between them, Hakeem Nicks, Domenik Hixon and Rueben Randle had eight balls thrown their way. Only Nicks came down with one, and that for only 10 yards. Randle missed opportunity after opportunity.
While New York's play overall was uninspired, its receiving corps looked especially flat, failing to come back to the ball, exhibiting sloppy route-running and not finishing the play.
Manning, for his part, needs to keep pushing the envelope, though, spreading the ball around.
The Giants won four straight because Manning was generous with the football and because each week a new receiver showed up on the leaderboard and on the highlight reel.
That diverse attack must come back, and quick, for the Giants to stay among the elite in the NFC.
Isaac Redman looked like Adrian Peterson against Big Blue's defense on Sunday, running for 147 yards and a score.
The Giants' run defense, which had improved dramatically over last season, fell back into old habits Sunday, overpursuing, arm-tackling and lacking a sense of urgency to the ball.
If teams are allowed to eat up the clock and control the game like Pittsburgh did Sunday, then Eli Manning and the offense will forever be playing catchup and be forced into passing early and often.
If New York wants to avoid a midseason slump, which has become the norm during the Coughlin era, it needs to get back to basics quickly by improving its reads, allowing the play behind the line to unfold, then chasing the ball with tenacity once their opponents have committed to a play.
This should be fairly easy against the bungling Bengals, who look like a team on their way to the division cellar.
But stopping the run against an AFC weakling won't get you to the Super Bowl, and it won't keep your offense sharp all year.
The Giants need to step it up and maintain that effectiveness for their post-bye schedule, because if you give the Packers, Saints and Eagles any semblance of a running game, they will kill you in the air.
The Giants need to forget about Hurricane Sandy.
That's easier said than done, but they must forget about it, at least come kickoff.
To varying degrees, the entire roster was impacted by Sandy. Some, like Eli Manning, saw their homes flooded, others had homes that sustained wind damage and some have been without electricity for a week, and on and on.
While enduring a hurricane is surely easier when you're a millionaire, the disruption to one's schedule and to one's routine will still affect your performance, as was evidenced by the Giants' performance on Sunday.
Big Blue must move on and be single-minded on the football field every day this week, leading up to Sunday's matchup with the Cincinnati Bengals.