INDIANAPOLIS -- Evaluating draft prospects is an inexact science. That is only magnified when the players can’t work out at the NFL combine or pro days.

Injuries will prevent Mississippi State defensive tackle Jeffery Simmons and Oklahoma wide receiver Marquise Brown from providing any measurables, which makes the evaluation process even tougher.

Brown recently underwent surgery to repair a Lisfranc injury; Simmons suffered a torn ACL during training. Tennessee Titans general manager Jon Robinson is tasked with figuring out if selecting a top prospect coming off an injury is worth the risk of potentially lost playing time.

"Certainly the film speaks for itself, but we will talk to those players and see how they are feeling and where they are at," Robinson said at the combine. "You have to weigh it. You can get a really good player but know you might not have him for a little bit of time because he's recovering. That's something that myself, [Titans] coach [Mike] Vrabel and the doctors will have to search through."

Robinson has selected a player without seeing him take part in pre-draft workouts in the past. He took Corey Davis at No. 5 overall in the 2017 draft despite not having any combine or pro day workout to use in the evaluation process. Vrabel said that experience could come into play when evaluating Brown and Simmons.

Vrabel added: "If a guy is injured and he isn't going to work out through his pro day, I am sure Jon [Robinson] has a plan. We just have to go to the film to see what his game speed is and what his play speed looks like."

Tennessee, which holds the No. 19 overall pick, needs a disruptive interior defensive player to pair with Jurrell Casey. Before tearing his ACL, Simmons was rated as the No. 4 prospect on Todd McShay's top-32 list. McShay credited Simmons for playing with natural leverage and improved hand usage. Simmons' 17 tackles for loss provides evidence of his ability to make plays in the opposing team's backfield.

The 6-foot-4, 300-pound defensive tackle plays with a high motor, at times tracking down running backs on screen passes and running down ball carriers on plays that are designed to go away from him. Vrabel likes players who "love football, are competitive and play hard."

Things get trickier when evaluating Simmons, who was captured on video hitting a woman and later pleaded no contest to simple assault. The interview process will be important for Simmons, who was not invited to the combine because of the incident.

Vrabel said he won't count out players who have off-the-field issues in their backgrounds.

"We all make mistakes. That's the first thing. Things are going to happen," Vrabel said. "Is it a mistake or is he a bad person? If it's a mistake, you try to fix the mistake. If the guy is a bad guy, then you move on."

Simmons hasn't had any other off-the-field issues and, according to Mississippi State defensive-line coach Brian Baker, has evolved into a leader during his time in college.

The Titans are also in need of a dynamic playmaker like Brown, who averaged 17.6 yards per reception last season and scored 10 touchdowns. Teams will want to know whether Brown can regain the speed he showed before the foot injury.

"You rely on the doctors to give you the best prognosis they can and look historically at players at their respective positions," Robinson said. "How did they come back from those injuries and what was their performance level like?"

One example is former Steelers and Jets wideout Santonio Holmes, who was 28 when he suffered a Grade 4 Lisfranc injury (the most severe) in Week 4 of the 2012 season. He was able to return in 2013 with 23 receptions for 456 yards and a touchdown.

It's unknown how severe Brown's injury was, but at 21, he's expected to be ready for training camp.