2015 Steelers depth chart: Stephon Tuitt's improvement could spell the end for Brett Keisel

The Pittsburgh Steelers hit free agency hard last year, bringing in a handful of veteran players to earn starting roles and improve depth.

Here is a position-by-position look at the Steelers depth chart going into this year's March 10 start of free agency.

PITTSBURGH -- The Steelers defensive ends will be better this year, as future Pro Bowl player Cam Heyward and rising star Stephon Tuitt hold down the corners.

Many believe that Heyward, the Steelers No. 1 pick in 2011, already is a superstar. And he likely will be paid accordingly after this season. Heyward's four-year rookie contract worth $6.705 million ends a year from now, and he most assuredly will attempt to be re-signed before the end of training camp.

Heyward was sixth among Steelers defenders in tackles, not an easy task while playing in a three-four defense, including 7.5 sacks, 21 quarterback pressures and four pass breakups. Heyward is extremely valuable, and after Roethlisberger's new contract the Steelers should move quickly to sign him.

An afterthought when the season began, Brett Keisel -- like James Harrison -- was crucial to the Steelers defense making it through the season. Sure, that unit was suspect on the back end, but played decently up front thanks to Keisel and Heyward, as well as the emergence of rookie Tuitt. In fact, Tuitt's improved play could spell the end for Brett Keisel, even though the veteran played pretty well before he was injured in Game 12.

It was the second straight season that Keisel missed four games, and there's no reason to believe that Keisel's body wouldn't continue to break down at age 37 (Sept. 19). He is signed for this season at $1.5 million, but it is unknown whether he will retire or attempt to come back for a 14th NFL season.

Steelers 2015 Depth Chart Review

Reviewing where the Steelers stand in terms of depth heading into free agency and the draft.

Tuitt gives the Steelers run-stopping and pass-rushing ability at both ends spots, so he could be a long-term performer opposite Heyward despite being the team's youngest player (22 on May 23). His cap hit this year is around $1 million, but he has three remaining years on his rookie deal after being the club's second-round pick in 2014.

Two other veteran ends on the defensive line might not return for next season. Clifton Geathers was signed when Keisel was injured, but he couldn't even get on the field in every game. And Cam Thomas, who was signed as a free agent last year to provide depth, had a poor season and could be cut to save the Steelers about $2 million. For a player supposedly able to play both end and nose tackle, Thomas could play neither with any consistency.

So, once Tuitt started to come on, Thomas was moved out of the starting lineup and nearly out of the rotation. Three other defensive ends signed future contracts. Matt Conrath played collegiately at Virginia and has been in the NFL for three seasons. Ethan Hemer was a rookie from Wisconsin, and Joe Kruger was a first-year player from Utah.

The 6-foot-7, 308-pound Conrath spent the past three seasons with the St. Louis Rams after signing as an undrafted free agent in 2012. He has played nine total games, with eight coming in 2013, but he spent the majority of last season on the team's practice squad.

Hemer is listed at 6-6, 282, but he actually is about 20 pounds heavier, so he gives the Steelers more size up front as well. Hemer spent last spring with the Steelers as well after a successful career with the Badgers where he blossomed after beginning as a walk-on. He was on the Steelers practice squad most of last season.

Kruger, the brother of Cleveland Browns outside linebacker Paul Kruger, was taken in the seventh round by the Philadelphia Eagles in 2013. A shoulder injury late in the preseason cost the 6-6, 290-pound Kruger his rookie season, as he was placed on injured reserve. He spent some time with the Eagles, San Diego Chargers and Green Bay Packers last year before winding up in Pittsburgh. He has not yet played an NFL game.