As for the slot position, the Cowboys coaches are very high on Blake Webb and have been for a long time but injuries have kept him on the shelf. Now is a good time for the 5-11, 190-pounder from The Woodlands to find a steady stream of health.
Also, Glidden has experience playing in the slot. Redshirt talent Ra'Shaad Samples is one of the faster players on the team and should be ready to step into a regular role. I think you could see C.J. Curry flash some inside and present a "Blake Jackson" style of option at the inside position. For various reasons, Jackson wasn't able to work out on a regular basis but Curry has been coming along rapidly throughout the second half of the season showing big improvement in practice and impressing the coaching staff.
Finally, in the 2014 recruiting class there is a junior college transfer in the speedy Tyreek Hill, who was mentioned as a punt return possibility. He is coming to Oklahoma State primarily because the Cowboys said he could play in the slot and now they may need him more than even they previously imagined. He is a natural to play there with his speed and ability to make plays in space.
Also, freshman James Washington might just be a player that could help out immediately. He reminds me of a bigger Josh Stewart coming out of high school where he helped Stamford to the Class A state championship.