Tomas Jurco hasn't played a game since Detroit's October 30th loss to Ottawa, and as of today he's been assigned to Grand Rapids for a conditioning stint. There's been a lot of speculation as to why he isn't playing. The only comment Jeff Blashill has made is that he needs Jurco's skating to be at a higher level. This has led to a lot of speculation that Jurco just isn't meeting his coaches expectations, but it's also opened the door very quietly to the possibility he's still fighting some nagging health issues that are negatively impacting his play.
While this isn't definitive proof, this actually lends some credence to the idea that Jurco may have been working through something. The CBA is a little murky on what is allowed for conditioning stints. Here's Article 13.8:
Conditioning Loan. Unless a Player consents, he shall not be Loaned on a Conditioning Loan to a minor league club. Such Conditioning Loan shall not extend for more than fourteen (14) consecutive days. The Commissioner may take whatever steps he deems necessary to investigate the circumstances under which a Player is Loaned on a Conditioning Loan. If the Commissioner has reason to believe or determines that the Club has used the Conditioning Loan to evade Waivers, or otherwise Circumvent any provision of this Agreement, he may take such disciplinary action against the Club, as he deems appropriate. The Player shall continue, during the period of such Conditioning Loan, to receive the same Paragraph 1 NHL Salary, and be entitled to the same benefits, that he would have received had he continued to play with the Club.
This is a little hazy on whether or not you can send a guy down merely because he hasn't played in awhile, but there is a precedent to the NHL rejecting waiver stints for that exact reason. This would suggest (although not prove) that there has to be some sort of health issue damaging a player's ability to play.
Whatever the cause for Jurco's absence has been, the team apparently plans to return Jurco to the lineup in some fashion fairly soon, or else they likely wouldn't be bothering with this in the first place.