All week, we're examining the most interesting position battles entering USF's spring practice, which begins Monday.Today: middle linebacker (On deck: running back)2017 starter: Auggie SanchezThe consummate over-achiever, Sanchez exited the program as the school's career tackles leader (388). Despite his limitations (in terms of agility and fleetness), he may rank among the Bulls' career leaders in grit. The de facto quarterback of the defense the last three seasons, Sanchez's value in terms of leadership and locker-room presence can't be quantified.2018 starter: At his signing day press conference a few weeks back, Coach Charlie Strong essentially challenged senior Jimmy Bayes, technically listed as Sanchez's backup last season. Once a four-star recruit (per Rivals.com) from Immokalee, Bayes recorded all of his nine career tackles in 2017. "You won't find a better-looking player than Jimmy Bayes," Strong said. "But Jimmy's got to step up now that we've lost some guys." We don't know if redshirt sophomore Andre Polk Jr. is fully recovered from last season's knee injury (perhaps we'll find out Monday), but this onetime four-star prospect (per 247Sports) presumably will be in the mix if healthy. Also expect sophomore Keirston Johnson — a former three-star guy presumably beefier after a year in the program — to get a serious look. "Once we get into spring practice there's gonna be some guys that we move around," Strong said. That opens the door for some real experimentation. Last season against UCF, Strong slid safeties Khalid McGee and Devin Abraham in the box in dime packages, and it neutralized the Knights for a time. Could we see OLB Nico Sawtelle move to the middle, allowing Strong to employ McGee or another outside 'backer? Lots to sort out here.