Five things you need to know about the Lions:

1. Crunch time: General manager Martin Mayhew and coach Jim Schwartz are entering their fifth year together. They made the playoffs in 2011 and are 12-36 in their other three seasons. The Ford family ownership is known for exceptional patience, and Schwartz has a contract through 2015. (The terms of Mayhew's deal aren't known.) But there was some internal discussion about ousting Schwartz after last season, according to ESPN's Chris Mortensen, and missing the playoffs for the fourth time in a five-year tenure would put the jobs of both Schwartz and Mayhew in jeopardy.

2. Both lines are overhauled: The Lions will have three new starters on their offensive line and have swapped out almost all the defensive linemen they once packaged around Ndamukong Suh and Nick Fairley. On offense, 2012 first-round draft pick Riley Reiff has taken over at left tackle, but only after the team was unable to draft someone else to fit the position. Competition for the right tackle and right guard jobs extended well into the preseason, although the Lions hope that rookie Larry Warford will soon take over at right guard if he can't immediately. Defensively, the Lions looked to get longer and taller at defensive end by drafting Ziggy Ansah and Devin Taylor and signing Jason Jones and Israel Idonije. Ansah and Jones are expected to start. Based on the preseason, at least, Suh and Fairley are poised for monster seasons.

3. Special teams have gotten a makeover: The Lions finished 2012 ranked No. 30 among NFL special teams both by Football Outsiders and longtime Dallas Morning News writer Rick Gosselin. As a result, they have a new place-kicker (David Akers), a rookie punter (Sam Martin) and a new special-teams coordinator (John Bonamego). They have also moved on from returner Stefan Logan and carried a competition for both kickoff and punt returner deep into the preseason. Akers struggled with injuries last season with the San Francisco 49ers, but he'll have the advantage of eight indoor home games and it's expected that Martin will handle kickoff duties.

4. Reggie Bush's impact: There is little doubt that the new tailback will have a huge effect on the Lions' passing game, serving as a de facto No. 2 receiver. He'll gobble up all the underneath space created by receiver Calvin Johnson. Bush led the team with 10 receptions for 147 yards in the first three preseason games even though Johnson hardly played. The real question is whether Bush can elevate the Lions' running game, especially between the tackles. He proved more capable of handling that role in two seasons with the Miami Dolphins, and the Lions need someone -- Bush or perhaps backup Joique Bell -- either to draw down defenses into the box or capitalize more consistently when they surround Johnson with exotic coverages.

5. Matthew Stafford's time: The Lions' quarterback has thrown for 10,005 yards in the past two seasons, recently turned 25 and signed a new contract that will keep him in place for at least three more seasons. Despite those accomplishments, there is a sense that he has plenty of room left for growth. His mechanics have been analyzed from every angle, and his drop in completion percentage and touchdowns last season caused some concern. More than ever, Stafford has an opportunity to make the jump from above-average starter into a more select class.

-- Kevin Seifert, ESPN.com

Matthew Stafford attempted the most passes for the second straight year last season, but he threw 21 fewer touchdowns than in 2011. Since the NFL moved to a 16-game schedule in 1978, Stafford and Peyton Manning are the only two quarterbacks who have had that large of a drop-off between consecutive seasons in which a quarterback started every regular-season game.

Part of the decrease in touchdown passes was an increase in rushing in the red zone. The Lions dropped back to pass 61 percent of the time last season in the red zone after doing so 69 percent of the time in 2011.

Another reason behind the dip was timely tackling. Lions receivers were tackled 23 times at or inside the opponent's 5-yard line last season, most in the NFL. Calvin Johnson was tackled an NFL-high eight times inside the 5-yard line last season, six more than his 2011 total.

• Johnson has had no problem going over the middle to gain his yards. He has gained 1,000 yards on passes thrown between the painted field numbers two of the past three seasons. No other NFL player has done it once in that time.

• When safety Louis Delmas was off the field last year, opponents posted a 96.6 Total QBR on passes thrown 15 or more yards downfield, almost six rating points worse than league average (90.8). When Delmas was on the field, the Lions' defense allowed a 79.7 Total QBR on those throws.

-- ESPN Stats & Information