According to multiple sources around the league, the Steelers have used their restricted first round tender on Willie Colon. The reports are preliminary right now, but this could work out very well for the Steelers.
From my understanding, an NFL tender is a way of protecting yourself from losing a restricted free agent. A club first makes a qualifying tender offer. There are four tender amounts. Colon can either accept the offer, or negotiate with another club for a better deal. Were Colon to receive an offer sheet from a club other than the Steelers, Pittsburgh would a chance to match that offer first -- hence the 'restricted' status. If the Steelers were to decided not to match another team's offer, they would receive draft picks in compensation. The highest tender amount yields a first and third round pick, while the second highest receives just a first. It's not clear yet which tender Colon was offered.
We'll see if Colon decides to accept or reject the tender, but it wouldn't be surprising if he decides to shop elsewhere. If he rejects it he puts himself at risk for earning less than the tender is worth, which is upwards of $3 million dollars. But even though he's coming off an Achilles injury, it's not all that realistic that he wouldn't command a more appetizing deal than what he'd be compensated for in Pittsburgh. More on this development as details become available.