Football is a grown man's game. And for the most part that's who the Dolphins will rely on this season.

But at a few key positions the Dolphins will rely on youngsters, second-year players or rookies – quarterback (Ryan Tannehill), left tackle (Jonathan Martin), running back (Lamar Miller), right defensive end (Dion Jordan and Olivier Vernon), and, most likely, kicker (Caleb Sturgis).

If these guys don't produce the Dolphins will almost surely miss the playoffs for a franchise-record fifth consecutive season.

"I know that we're not there yet," Tannehill said. "We have a long way to go, and we're going to use the fall camp to our benefit and get better each day."

Everything starts with Tannehill. He enters Sunday's first practice of training camp with a full season as a NFL starter so theoretically he should do better than the 12 touchdowns and 13 interceptions he had last year as a rookie.

Tannehill has been given significantly better talent among wide receivers Mike Wallace and Brandon Gibson, and tight end Dustin Keller, and the Dolphins hope that makes a difference.

Last season Tannehill finished 27th in passer rating (76.1), which was just one spot below Indianapolis' Andrew Luck (76.5). Tannehill flashed moments of brilliance. He was 21-for-29 passing for 185 yards, two touchdowns and no interceptions in a 17-14 victory against St. Louis.

But all too often he had games such as the Nov. 15 game at Buffalo when he went 14-for-28 passing for 141 yards, one touchdown and two interceptions. The fact remains Tannehill is still a youngster and needs help.

Two of the guys charged with taking pressure off Tannehill, Martin and Miller, are also second-year players.

Martin, who flips from right tackle to left tackle and is now protecting Tannehill's blind side, was rated 76th among 80 offensive tackles last season by ProFootballFocus. With most opponents he'll be tasked with blocking the team's best pass rusher. If Martin fails, the Dolphins' revamped passing game will also fail.

To a certain extent that's also true at running back. Miller, the former University of Miami standout, averaged 4.9 yards per carry last season (250 yards on 51 carries) in spot duty behind veteran Reggie Bush. There's little doubt about Miller's running skills, but his pass protection is questionable.

"We like a lot of the things he is doing in pass protection," coach Joe Philbin said after off-season practices concluded. "Again, we have to temper our enthusiasm based on how he does in pads, but I think his understanding of how he fits in the protection scheme is very good."