Isles add Seidenberg, Now What?

According to reports the Islanders have agreed to terms with former Boston Bruin and current European World Cupper, Dennis Seidenberg on a one year, one-million-dollar deal.  Seidenberg has spent the last six plus years in Boston, where he was bought out of the remaining two years on his contract in June, which made him an unrestricted free agent this summer.  Seidenberg played 61 games last season and still average almost 20 minutes per contest.  As a 35-year-old defenseman he has been brought in to provide depth to the back end.
According to Pierre LeBrun of ESPN and TSN there were 8-9 teams that were interested in signing Seidenberg during a well-played World Cup by him. This leads me to believe that he was brought in here as more than a 7^th defenseman.  While he is 35 he is by no means over the hill.  The Bruins are a team that has had many cap issues over the years, (as noticed by the Boychuck trade two years ago) which should be taken into account on why the Bruins no longer needed his services.
On the surface, this is a good deal by the Islanders.  They added a player to their team that will make them better at least in the short term.  I can’t help but think this will have adverse effects on Ryan Pulock and his attempts to make the team.  One thing we know about young defenseman, is they make mistakes.  With Seidenberg now, I expect the Islanders to be less patient with those mistakes.  If Seidenberg was truly brought in here to provide competition but ultimately be the 7^th defenseman this is a great move because it provides depth in case one of the top six goes down or someone is struggling to the point they can’t be on the ice.  I have trouble believing that he will be in that role and would not be surprised if that means Pulock is going to start the season in Bridgeport.
Currently the Islanders have 23 players on one way deals which means they would need to pass through waivers in order to go to the AHL.  Ryan Pulock can go down to the AHL without going through waivers.  Possible waiver candidates include Alan Quine, Scott Mayfield (who both signed one way deals in the offseason), and JF Berube.  Dennis Seidenberg makes this team better in the short term but is he a long term hindrance?