(973espn.com) - There is a science to building a championship-level roster in the NFL and the Eagles have tapped into the most obvious formula, finding the franchise-level quarterback and building the foundation up around him in the trenches on both sides of the football.

The strengths of the Eagles since they have become a legitimate Super Bowl contender have been at the QB position -- be it the MVP-level Carson Wentz in 2017 before the Mariano Rivera-esque closing skills of Nick Foles took over -- and both the offensive and defensive lines where a host of Pro Bowl-caliber talent has resided.

From there the way you fill in the roster usually depends on circumstance.

The commonly-perceived thought that Philadelphia does not value the running back position has some merit to it but like all things in life needs the context added, namely that the entire league had downgraded the position as a whole in the modern era where the passing game has made getting the QB or getting to the signal caller of paramount importance.

It's easy to see what NFL teams value by looking at the annual franchise-tag numbers, which tell you the most valuable positions in the league are QB [get the signal caller], followed by edge rusher [get to the QB]. Running back, once the glamour position in earlier eras of the game, is now less valued than any other position with the exception of tight ends, safeties and specialists.

And if you actually defined TEs better by splitting the true slot threats from the traditional Y-backs or in-line players and adjust your thinking with the current safety market as evidence, it's now plainly obvious that the only thing less valuable to most NFL teams than their RBs is a blocking tight end and those specialists.

There are always exceptions to the rule, however, so while most are quick to cite than the last RB the Eagles selected in the first round was Keith Byars back in 1986, they usually fail to add the context that Christian McCaffrey would have been the pick at No. 14 overall in 2017 had he dropped to Philadelphia.

McCaffrey, however, is a very unique player, a true three-down threat who ran routes better than some receivers at the NFL combine when he was coming out of Stanford. In other words, it's not easy to get a back like CMac so when he's not there the Eagles are going to default to more important positions who can have a greater impact of the game like their actual choice in 2017, defensive end Derek Barnett.

By definition, Philadelphia has already proven they can win a Super Bowl with a committee approach at RB and that's going to continue until they get a player capable of handling the job description of a true three-down back.

The current committee is thin, though, one projected to be led by Corey Clement, Josh Adams and the ultimate afterthought entering his fourth season, Wendell Smallwood at least until reinforcements are added.

“You talk about Corey [Clement], a guy who was a huge part of our Super Bowl winning team and our Super Bowl win. Josh Adams showed in flashes what he can. Obviously, those guys coming off offseason injuries and a big part of that is getting them back and getting them back as part of the program," Eagles executive vice president of football operations Howie Roseman said at the annual league meetings in Phoenix on Monday. "For Josh, that jump from year one to year two is big; Corey from year two to year three. You also have to talk about Wendell. When Wendell’s been called upon to play he’s been a solid player and has played well for us. Boston Scott has all the tools in his body, traits to develop. There are young players there, but at the same time we’re always looking to improve the team."

The Eagles will add at the position but whether that comes in the second phase of free agency or the draft remains to be seen. The team's top target in free agency, Tevin Coleman, opted for the familiarity of a Kyle Shanahan offense in San Francisco while Jay Ajayi, still rehabbing a torn ACL, could be a fallback.

"We had three running backs who played in the Super Bowl [LeGarrette Blount, Clement and Ajayi] were guys we all acquired after the 2017 draft, so the talent acquisition period continues to go," Roseman said. "We want to have the best possible team. We’ll look into everything, that’s our job, but at the same time we have to grow and develop our younger players.”

The draft is thin at RB with only Alabama's Josh Jacobs as a potential option at No. 25 overall. The second round, where the Eagles have picks 53 and 57, could be prime real estate as well. Back when the team wanted McCaffrey it also had a keen interest in Dalvin Cook before Minnesota leaped ahead of the Eagles to take the former Florida State star in the second round.

“I just go back to our history over the last couple of years, we’ve been fortunate to win a lot of games with the running backs we have on this roster, and have opportunities also to acquire backs, not only before the draft but after the draft process,” said Roseman. “So we’re going to continue to look at every position, ways to improve our football team. We want to be as good as possible at every position, but it will not put us in a position at any spot where we’re forcing something in the draft because that’s where you make mistakes.”

According to Roseman, it's all about versatility but a true three-down back is becoming the white wale of the current Eagles regime.

"You have to be versatile and open to every opportunity that comes in front of you, so when you have a plan, you can have a plan A, but when that goes a different way or people get a different amount of money or you have other opportunities that (are presented) you have to be flexible enough to say I know what I thought on March 13 (when free agency began), but this really helps our football team and this improves our football team," Roseman explained.

-John McMullen covers the Eagles and the NFL for 973espn.com. You can reach him at jmcmullen44@gmail.com or on Twitter @JFMcMullen