Rating Titans' depth by position

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NASHVILLE, Tenn. -- Depth issues helped kill the 2015 Tennessee Titans.

Quarterback Marcus Mariota missed four games with two knee injuries, and Tennessee lost all four games started by since-departed Zach Mettenberger

Starting outside linebacker Derrick Morgan missed six games and wasn’t himself in a few others before he landed on IR with a shoulder injury. Receiver Kendall Wright also missed six games. Cornerback Jason McCourty played in only four games because he twice needed surgery to repair a sports hernia. Staring center Brian Schwenke only played in the first six games before an ugly injury sent him to IR.

The Titans experienced significant drop-off in every replacement situation.

Upgrading the top of the roster has been a priority -- the team looks to have four new starters on offense, one new starter on defense (and two additional newcomers in the nickel set).

But the depth is better as well, at least at spots.

Linebacker is one spot that looks to have found some answers with Sean Spence, who plays in the nickel and adds something to the inside linebacker group, as does veteran Nate Palmer and the 33rd pick in the draft, Kevin Dodd, who will make his preseason debut Saturday in Oakland.

The receiver group still has question marks, but is deeper with two new starters -- Tajae Sharpe and Rishard Matthews -- and the addition of veteran Andre Johnson.

"I think we're deeper in some areas," head coach Mike Mularkey said.

But there are other spots that still need sorting out.

"I think we still have time -- we still have a couple weeks here," he said. "We got a good week of work. We won't be able to do this next week, because it's a short week, but we still have some time to figure out where we are with our depth."

Here is a position-by-position rating of the Titans depth, from deepest to shallowest.

Defensive line: The Titans have spent some draft resources here and have a pretty deep pool beyond starters Jurrell Casey, Al Woods and DaQuan Jones. They are high on Angelo Blackson. Though second-round pick Austin Johnson is a third-teamer right now, he’ll grow. Karl Klug can be disruptive, and two undrafted rookies are making noise with nose Antwaun Woods ahead of Johnson and Mehdi Abdesmad making a bid for Ropati Pitoitua's spot.

Linebacker: Brian Orakpo and Morgan man the outside with Avery Williamson and Wesley Woodyard inside, and Spence taking over for Woodyard in nickel. Dodd hasn’t played yet, but should be a major boost to the pass-rush depth. We’ve seen preseason plays from Palmer, Curtis Grant, David Bass, Deiontrez Mount and Justin Staples. Another versatile backer, rookie Aaron Wallace, just got back to work after an early camp high-ankle sprain. This looks much better than last season, when lack of depth was a major issue.

Tight end: Very solid top three with Delanie Walker, Craig Stevens and Anthony Fasano. Phillip Supernaw needs to be sure to be penalty-free on special teams, but he can make some plays when called on.

Running back: The Titans are two-deep for sure, with DeMarco Murray and Derrick Henry poised to lead a team determined to run. After that is nothing special, with Dexter McCluster overrated by Mularkey, and Antonio Andrews, David Cobb and Bishop Sankey fighting for the last spot or spots.

Receiver: It’s hard to look at a group that has struggled so much over the years and claim it’s deep. But Sharpe has been special and Matthews should be steady. Once healthy, Wright can be productive out of the slot. Johnson and Harry Douglas bring some veteran savvy, and Tre McBride makes catches and can be an important special teamer if he sticks. It’s gotten deeper for sure.

Quarterback: Very few teams feel great about the chances to maintain their level of play if the starter goes down. The Titans are set with Mariota as the man. Matt Cassel has played a lot in the league, but his recent work has been poor.

Defensive back: The safety depth is actually good. They have five that are worth keeping. But the cornerback situation is bad. Antwon Blake has ranked fourth, started last week with McCourty and Perrish Cox out, and was terrible. Said Mularkey of Blake: "Antwon has a role here. Probably not the starting corner against starting receivers." The team’s fourth cornerback has to be capable of starting against starting receivers. No one is standing out much from the rest of the group, with fifth-rounder LeShaun Sims probably the best of the lot.

Offensive line: They traded receiver Dorial Green-Beckham for Dennis Kelly, who ranks as the sixth offensive linemen because of his versatility. Starting left guard remains a question mark. Two guys still in the mix there are likely roster locks. But rookie guard Sebastian Tretola is over-aggressive, and former starting center Schwenke has been hurt a ton.