SANTA CLARA, Calif. -- For as often as San Francisco 49ers general manager John Lynch and coach Kyle Shanahan have discussed the need to find a franchise quarterback, another key piece of the team's rebuild has flown mostly under the radar.

While the quarterback is undoubtedly the centerpiece of any offense, various defensive schemes require different players to serve as the foundation. As the Niners transition to coordinator Robert Saleh's 4-3 defense, one position that is an absolute priority is free safety.

In speaking to Bay Area media for the first time earlier this week, Saleh acknowledged that his scheme, which is similar to Pete Carroll's system in Seattle, relies heavily on a single high safety. Among the reasons the Seahawks have had so much success in recent years is the presence of free safety Earl Thomas.

Players like Thomas don't grow on trees, but finding a reasonable approximation would go a long way in jump-starting a turnaround for a defense that ranked last in the NFL a year ago in yards allowed per game.

Converted cornerback Jimmie Ward probably won't be the next Earl Thomas, but the 49ers hope he can fill a similar role. Kyle Terada/USA Today Sports

"One of the really cool things for me is the system we have is kind of a good road map of what you’re looking for," Lynch said. "Not that it’s a cookie cutter, but everybody would love to find Earl Thomas. There’s not many of those guys out there and it doesn’t mean that we’re looking for a 5-9, 195-pound guy like Earl is, but we’re looking for some of those traits.

"It’s a credit to Earl. He’s put it out there that this is the profile you’re looking for when you’re playing this scheme. We’re going to make this scheme our own scheme and we’re going to have some wrinkles that they don’t have, but that position is pretty defined as to what the standard is."

It's a lofty standard and players of Thomas' caliber are coveted by the rest of the league as well. But the Niners are putting a premium on it because of what Saleh will ask of the position in his defense. In the system, the free safety is often the only player on the back end of the defense, with the strong safety playing closer to the line of scrimmage to help stop the run. Like a center fielder in baseball, the free safety must have the speed to cover a tremendous amount of ground and the instincts to know where to go on a given play.

As it stands, the Niners simply don't have many options to fill that void. Lynch said Wednesday the only player on the current roster who could get a look at free safety is converted cornerback Jimmie Ward.

"I think Jimmie is going to get his chance and that’s something we’re excited about seeing," Lynch said. "I think even for great players, people have always said that’s an easy transition, if he can play corner, he certainly can play safety. It doesn’t always work like that because you see the position a different way. We’re going to vet that, we’re going to look at it. We don’t know. I don’t think Jimmie knows, so we’ll see."

While Ward hasn't played much safety since he arrived in the NFL in 2014, he did play safety at Northern Illinois. Throughout Ward's career, some have wondered if he would ever get a chance to play free safety, the position some analysts believed was best for him entering the draft.

At 5-foot-11, 193 pounds, Ward is similar to Thomas in size and his unofficial 4.47 times in the 40-yard dash at his pro day were close to Thomas' official 4.49 time at the scouting combine. Of course, there's no way to account for the instincts and reaction time that make Thomas one of the league's elite defensive players.

Still, Ward at least will get a chance to show the Niners if he's capable of making the move before he's written in ink on the depth chart.

“The good thing about Jimmie is he’s capable of doing both, which is a credit to him," Shanahan said. "In fairness to him, I want to make sure we put him at the best spot that is his best position, and I don’t think we have that answer yet. The good thing about him is he can help our team in either way. We think he can play at a high level at both positions, but that’s something that’s going to have to do with how he ends up showing us in practice and how our roster ends up panning out.”

Therein could lie the rub. Although rangy free safeties are hard to find, this year's draft looks to have some intriguing candidates. Ohio State's Malik Hooker has the physical traits and tape that make him an ideal candidate to fill the role, though there are questions about durability and sample size. He's projected as a top-10 pick, meaning if the Niners wanted to pursue him, they'd have to take him at No. 2 overall or in a small trade down.

To this point, there have been no reports linking Hooker and the 49ers, but the Niners did host Washington's Budda Baker for a pre-draft visit. Baker has been compared to Thomas in his own right, in part because of his proximity to the Seahawks and their similar builds. Draft analysts see Baker as more of a second-round pick though he could sneak into the late part of the first round.

Whether it's Ward, Hooker, Baker or someone else, the Niners' search for a free safety will be one to watch in the coming weeks. And while a determination on Ward's viability at the position can't be made in a short minicamp just before the draft, it will at least offer some clues.

"We’re going to do what we think is best for our team, and Jimmie, I think, provides a unique versatility and we’re going to try to take advantage of that," Lynch said.