Alexander, one of five players available in the draft, received a clean bill on his drug tests, according to Mike Garafolo of the NFL Network.
There have been character concerns surrounding Alexander, who was dismissed from Virginia Tech in May due to academics. Alexander also was arrested on a marijuana-related charge in 2016, but he has passed all of his drug tests over the past eight months, Garafolo reported.
Alexander, Western Michigan cornerback Sam Beal and Mississippi State safety Brandon Bryant are considered the top players in the supplemental draft. Oregon State linebacker Bright Ugwoegbu and Grand Valley State running back Martayveus Carter are also available.
NFL DraftScout.com senior analyst Dane Brugler wrote that "Alexander has NFL starting potential once he receives more coaching, but questions regarding his football and personal character cloud his projection."
The 6-foot-3, 207-pound Alexander started 15 of 34 games over three seasons at Virginia Tech, recording seven interceptions. He was expected to vie for a starting job in 2018 prior to his departure.
"Alexander has intriguing talent with his combination of size and athleticism; teams with schemes that place a premium on length at cornerback will be particularly interested," Brugler predicted. "Other teams will view him as a safety with his range and toughness vs. the run while his hiccups in coverage will be minimized."