2015 NFL training camp: Arizona Cardinals injury update, Niklas and Gresham activated

On Monday, the Arizona Cardinals started the official part of football -- they put the pads on in training camp practice. But not everyone practiced. This is your injury update.

First, the good news.

The Cardinals activated tight end Jermaine Gresham from PUP and tight end Troy Niklas from NFI. That means they can practice. However, they weren't thrown in to the wolves just yet.

Head coach Bruce Arians said he wanted to get Gresham activated so he could start getting mental reps and at least participate in morning walk-throughs. They want to "gradually work him into football shape because it's taken him a while to get in shape."

Arians said it was like when the team signed John Abraham in 2013.

Niklas also can get the mental reps, but  he isn't quite ready for pads. He tweaked his hamstring training -- running routes. He will be doing some individual drills and hopefully practicing fully by the end of the weel.

Now for the part where people are hurt.

Running backs Andre Ellington and David Johnson sat out Monday's practice. Johnson pulled up with a limp after a fantastic run on Sunday. He is day-to-day with a hamstring injury. Ellington had hamstring tightness on Sunday and came out. He also sat out Monday.

The worst news was about rookie linebacker Shaq Riddick. He had a hamstring issue that kept him out of almost all the spring practices. He tweaked it again over the weekend and had an MRI. He has a Grade 2 tear, which means he will miss "some time." It might come to putting him on injured reserve if they need to make a roster move, but that won't happen until near the end of the preseason.