McDougle tore his ACL earlier this offseason.
He was a third-round pick in the 2014 NFL Draft.
There's been some confusion as to why McDougle and Shaq Evans (who went onto injured reserve yesterday) were able to be added to the IR list without first having to pass through waivers.
As I understand it, both players were simply added to the permanent injured reserve list and will therefore continue to count towards the roster limit for the time being. Other players this offseason have been waived/injured, which means a roster spot is freed up and the player can revert to injured reserve once they've cleared waivers. However, this is not without risk and the Panthers lost their rights to their sixth-round draft pick when New England claimed him a couple of weeks ago.
Once we get to August 27th, which is the point at which teams are required to cut down from 90 to 75, non-vested veterans no longer need to pass through waivers to land on injured reserve, so many teams would just wait until that point. However, for the Jets, this is merely a procedural move and these players will no longer count towards the roster limit after that date so that will be two fewer cuts they need to make to get to 75.
In theory, either of these players could be granted a designation to return during the season, but it sounds like both of them are out for several months, so I'd imagine they'll save that temporary IR designation for someone else with a less serious condition. Since Antwan Barnes has yet to practice, they have the option to leave him on the PUP list and preserve that temporary designation. However, from Rex Ryan's comments earlier in the day, he may be ready to return soon and this might lead them to want to get him back into practice.