One part of Marcus Mariota — the heart undoubtedly — wants him to jump into drills on both legs at Tennessee Titans’ organized team activities these days.

Even the right one, which is recovering from a fractured fibula.

“You know, it is close (to being healed) and I’m able to do a lot of things out on the field, which kinda sucks because I feel like I can be out there and practice (full-on) again,” Mariota sighed Wednesday after being held out of some drills. “But, again, I just have to stay the course and stay focused on getting healthy and I’ll be ready to go once the season begins.”

If that caution has sometimes been in danger of being overridden by Mariota’s competitive diesel drive, there was a sobering reminder for both he and the Titans Wednesday. Backup quarterback Matt Cassel will require surgery on his right (throwing) thumb to have a pin inserted after banging it on a helmet Tuesday. Cassel is expected to be out six weeks, the Titans said.

If Cassel could be sidelined by a freak injury in the padless OTA’s, the Titans undoubtedly shudder to consider what black cloud could befall their franchise player if they turned him loose. And, of course, what that would mean for 2017, a season of untethered hopes for the once hopeless franchise.

If the Titans could erect a protective bubble that Mariota could fire passes through, be assured they would.

As it is defensive linemen not only pull up well short of the one they call the “golden child” and “the franchise,” they sometimes dramatize it as if he had a protective field around him, as linebacker Brian Orakpo did recently. “It has been way over-exaggerated,” Mariota says, laughing.

But his importance to the Titans is no laughing matter. The 2014 Heisman Trophy winner and second overall pick in the 2015 NFL Draft carries the Titans’ hopes for return to the playoffs, a place they might have appeared last season if not for the fractured fibula suffered in Week 16.

ESPN analyst Jon Gruden sang Mariota’s praises in a media conference call — “Athletic … great kid … sharp, has all the things that I was looking for. … The only thing he hasn’t been able to do, in my opinion, is stay healthy. And that’s a challenge he’s gotta meet — and I hope he does.”

The Titans have painstakingly dedicated themselves to seeing that he arrives at their Sept. 10 season opener against Oakland not only passing sharp but in one healthy piece.

Offensive coordinator Terry Robiskie told reporters Thursday that the team medical staff, general manager and head coach meet regularly to decide Mariota’s availability for specific drills, number of repetitions and situations.

“They monitor how many snaps he takes. They monitor what snaps he takes, whether it is 7-on-7 (drills), team or individual. They monitor all his repetitions and then they sit down and talk about it,” Robiskie said. “Then, Todd (Toriscelli, Titans’ Director of Sports Medicine) basically says ‘he’s strong, he’s weak, give him a little more or back off a little bit. All we do as a coaching staff is sit down and say how many plays has he got? We just basically ask how many reps are they going to give him of this and for that and we go from there.”

Mariota said he is getting close to where we wants to be, “just being able to do roll-outs, do everything normal and just be the same guy, the player that I was. I think this is kind of the final step for me.”

He acknowledges that it is his nature to push, “but you can’t over-push it ’cause then I won’t be able to practice the next day. So it is kind of finding that fine line, that happy medium.”

For the Titans the “happy” part comes in keeping their quarterback — and season hopes — healthy.

Reach Ferd Lewis at flewis@staradvertiser.com or 529-4820.