Who do we risk losing at the end of the season?

See below from the NFLPA website. All 4 of his seasons have been spent on either active, inactive or injured reserve status.

Accrued Seasons – An Accrued Season is a season during which a player has been on full pay status (Active, Inactive or Injured Reserve List) for six (6) or more regular season games. However, a player who is on the Exempt Commissioner Permission List, the Reserve Physically Unable to Perform/Non Football Injury List, or the Practice Squad for any of the six (6) qualifying games will not earn an Accrued Season regardless of his pay status.

You just answered your question, kentish.

If he was on the practice squad for six games in his first season (I'm not sure), then he would not have earned an accrued season in his rookie year, giving him only three now instead of four.