1) Mykkele Thompson, safety
One of the players to draw great reviews so far in spring practice is Thompson, and that's great news for a secondary that is looking for more consistency at the safety spot despite the graduation of top safety Kenny Vaccaro. There are certainly some bodies there, especially if Quandre Diggs shifts back to safety as many people think. But even then, there's a combination of guys who have had bright moments and some struggles. Thompson has world-class speed for the safety position, and could excel if he can get more physical. Safety is such a key spot because good safeties snuff out plays before they become touchdowns, and Texas found out the reverse is also true multiple times last year. If Diggs does move, that opens up a cornerback spot for guys like Duke Thomas as well.
2) Cedric Reed, defensive end
Jackson Jeffcoat still has another year left at Texas's BUCK end spot, meaning that Shiro Davis is still a year away from emerging as a likely starting end for the Longhorns. But Reed's skill set puts him as a likely replacement for the departed Alex Okafor. Reed had some nice moments a year ago, but needs to show that he can be consistently excellent. Texas has a really good-looking group of defensive tackles returning, and Jeffcoat should again be an All-Big 12 candidate (if he can stay healthy). That leaves Reed's end spot as the lone question mark on what could be one of the Big 12's better defensive lines. He has the potential to do very well there.
3) Peter Jinkens, linebacker
Jinkens emerged in the second half of last season, existing primarily on speed and raw instincts. But while he certainly made some 'WOW' plays, Jinkens wasn't consistently the kind of assignment-sound linebacker that the Longhorns need at that position. With Jordan Hicks coming back, Texas immediately improves at one outside spot. But the competition for that other spot could be pretty heavy. Jinkens has the athleticism to be outstanding there. It will be interesting to see how he's developed at the position.