My reaction went something like this: "what just happened?"
Not because I was shocked (I would have been), but because I missed the kickoff trying to catch the end of the Broncos-Raiders game.
Just about everyone who saw the game and works on TV is panning the call. It's similar to Belichick going for it on 4th and 2.
I doubt Mike Tomlin knew these numbers (he's been quoted as saying he makes these decisions by going with his gut) before the attempt, but the onsides kick decision actually improved the Steelers odds of winning. At least according to NFL Stats guru Brian Burke.
Up by 2 points with 3:58 left against the Packers, Steelers head coach Mike Tomlin called for an onside kick. Was this a good decision?
When onside kicks are expected, they are successful only about 20% of the time. But unexpected onside kicks are successful a surprising 60% of the time. I think we can say this particular kick was certainly unexpected. And surprise onside kicks can be the most beneficial when a team is ahead late in the game. Possession is critical.
In this case, had the Steelers recovered the kick, they'd have a 1st down at about their own 40, which is good for about a 0.76 win probability (WP). An unsuccessful onside kick gives the ball to the Packers at the Steelers' 40, worth 0.58 WP for the Packers (which is 0.42 WP for the Steelers.) With a 60% success rate, the overall WP for the onside kick would be:
0.60 * 0.76 + (1-0.60) * 0.42 = 0.64
WPA conventional kickoff gives the Packers a 1st and 10 at their own 30 or so (28 is the average, 33 is the median). This gives the Packers a 0.46 WP, which is 0.54 WP for the Steelers.
The onside kick is the better decision by 0.64 to 0.54 WP.
These estimates are only league baselines, but they suggest it was probably a good call.
What's most interesting to me is that a failed onside kick is hardly certain death--a 0.42 WP. There was plenty of time for anything to happen--a stop, a turnover, or a score. And sure enough the Steelers gave up a touchdown but came back with one of their own.
Also, a successful onside recovery doesn't seal the game. The Steelers would still need at least two first downs to clinch the win. Essentially, the Steelers traded 30 yards of field position for the chance to keep the ball out of the Packers' hands.