First, I'd like to welcome one of my favorite players to twitter @Tpolamalu.  Not sure what worldly advice he will impart through that channel, but Steeler Nation is happy to see him there.His first tweet:Not really sure what all that means, but guess we'll find out.  I'm sure we'll all follow Troy to see what wisdom he has for all of us.Back to football...Last year, we saw just how important Troy, or lack thereof, was for our defense.  Opposing teams had a much easier time planning without Troy in the game.  The role of safety, both strong and free, is a little bit linebacker and a lot wide receiver.   The role requires speed, agility, athleticism and agressiveness.  It's arguably one of the most difficult positions to fill because it's hard to find a player that has all of those characteristics and can play in the same manner as a Troy, or even an Ed Reed.  The one thing you can say about both of them, where the ball is, so are they.  And they play completely different, yet at the same time, both are critical to each team's defense.What the Ravens now face is a gap due to Reed's injury.  I say the Ravens are the team to beat in the AFC North, but their one weakness will be also the strength, the aging, yet amazing defense.The safety position has evolved and become such a leading role on the defense over the last decade.  The play action game has changed the way teams view the role of safety, not to mention the changes in rules to protect QBs and WRs.  The safety is often both necessary for challenging the run and definitely as the last line of defense on the passing game.  There just aren't a lot of players like Troy. (Yes I still love you Ryan Clark, you're a baller too) It's not just his athleticism that makes Troy, Troy...it's his character, his commitment to the game, and most of all, his acknowledgment that Sunday is when he goes to work.  He's just a player.  It's who he is and what he does.I think I can speak for all of Steeler Nation when I say, ITS GREAT TO HAVE YOU BACK TROY! Now just stay healthy.  And say no to Madden game covers from now on.  I never want to see you on the cover of that game again.PS - training camp opens for the fans a week from today.  There are 95 on the roster as of today.  Get ready for the games,  "show us what ya got" (cue JayZ)...let's go!