When teams are eliminated from the playoffs, players continue to play, but without a shred of "if we lose, we get a higher draft pick" satisfaction. They're playing for their futures.
In some cases, a player's fate has already been sealed due to poor performance. In others, a team may need to make a tough choice on whether to keep a player at a certain contract, or renegotiate with the threat of a release.
A few players on this year's Steelers' teams do not have the assurance of being with the club the following year, and won't point out how not excited they are to read an offseason full of intrigue over who their replacement will be, and possibly in which round that replacement will be taken.
Hampton is scheduled to be a free agent in 2013, while Harrison and Keisel are both under contracts. The Steelers renegotiated Hampton's contract for the 2012 season, cutting off the final 2013 year, and accelerating the remaining balance of his contract to the 2012 season. He could sign back with the club, but odds of that aren't good, at the very least not before he gives other potential suitors a look.
The Steelers have a tough cap situation and with Hampton turning 36 this offseason, odds are far better, should he want to continue playing, another team would pay him much more than the Steelers would be willing to offer.
Depth isn't the best behind him, however, and it leaves the door open for his return. Slightly.
Harrison has far less likely of a chance - and neither have good chances of returning. The Steelers drafted Jason Worilds three years ago with the intention of doing exactly what Harrison did in 2004 - learn the position and eventually be groomed to take over the starting spot when the veteran above him on the depth chart becomes too expensive. Harrison took over for Joey Porter in 2007, and had a better career top to bottom. Worilds certainly has big shoes to fill, but with free agency of his own pending for 2014, Worilds could be an inexpensive starter at a position that's carried a huge cap number for Pittsburgh this season.
Keisel has an extremely difficult situation as well, much like Harrison. The Steelers have spent two first round picks in the last few years on defensive ends (Ziggy Hood and Cameron Heyward). While neither is at the same level as Keisel, Heyward (Keisel's likely replacement in the starting lineup opposite Hood) was drafted in the first round for a reason. There comes a point he's gotta get - and stay - on the field.
If it is indeed their last games, they've got 31 other teams to audition for, and will play as the outstanding players all three have been throughout their careers. They were all valuable and outstanding members of the Steelers' mini-dynasty of the new millennium, and have two Super Bowl rings each to prove it.