Drinkwitz, who is in his first year coaching the Tigers, declined to say how many of the 12 players have the virus, versus those who are being held out because of contact tracing.
"Out is out," he said. "Whether they got it or whether they contact trace, out is out. They can't be around us, so there's no reason to get into the numbers game and hype. It's just we're down 12 guys. It is what it is."
Drinkwitz said the 12 players are being held out as a result of Sunday's tests.
"We tested again today," he said. "So ... who knows? We'll see. But as of right now, yes, 12."
Daniels, a redshirt senior, played in two games last season. Massey is a redshirt freshman and former three-star recruit.
As for Missouri's opponent, Crimson Tide coach Nick Saban said Wednesday night that Alabama started testing its players daily on Monday.
"We just thought that it gives the players a peace of mind," Saban said. "It's the best thing for the players. It's the best thing for the program. We have the capabilities and resources to do it, so we're happy to do it."
Saban said Alabama had previously been testing its players three times a week.
"But we just decided this week that we would test our guys every day," Saban said. "With that, hopefully everybody feels safe and it will help the fact that maybe we won't have to quarantine some of these guys, minimize exposure."
At this point, Saban said he didn't know of anybody on Alabama's team that would "be out for sure" for the scheduled Sept. 26 opener against the host Tigers.
"We may have some injured players who may not recover enough to be able to play in the game. ... I'm sure when we get into game week and we figure out who can and who can't [play], we'll kind of let you know," Saban said.
ESPN's Chris Low contributed to this report.