The Detroit Lions open their season this Sunday at 4:25 against the Indianapolis Colts. There is a lot to watch for in any season opener but the Lions have a lot to look at after the off-season they had. Calvin Johnson has retired, General Manager Martin Mayhew and President Tom Lewand are not longer with the team, and new general manager Bob Quinn’s first free agent signings and draftees are about to hit the field. But here five things to keep a close eye on for the Lions in their season opener.

1) Deandre Levy’s return: Levy missed 15 games last year with a non-football injury that was never disclosed. He missed the first three games of the preseason this year but played in the fourth game looks ready to play in the opener. Before his injury he was one of the most important players on the Lions defense at the weak-side linebacker position. He should play an important role for the Lions defense this year if he can return to his pre-injury form.

2) Taylor Decker’s debut: The first round draft pick out of Ohio State will make his NFL debut at left tackle on Sunday. It’s very tough to tell what a player will look like based on his preseason performance, so this should be the first real look the Lions, and fans, will have at Decker. The Lions are hoping that Decker can be the anchor on Stafford’s blindside for years to come and this is the first test for Decker.

3) The passing offense: There is a Calvin Johnson sized hole at wide receiver for the Lions. They signed Marvin Jones in the off-season but he plays a different type of game than Johnson did. Jones is not the vertical threat that Johnson was and plays more of a possession game. Look for him to run short routes and then try and make guys miss after the catch.

4) Ezekiel Ansah’s Development: Defensive end Ezekiel Ansah was the best player on the defense last year and in his fourth season hem might be able to make the jump to become one of the best players in the NFC North and maybe even the NFL. He should the Lions primary pass rusher this season and if the Lions hope to make any sort of run at the playoffs, he’ll have to have a big season.

5) Matthew Stafford: Some people think that the veteran quarterback is going to sign the largest extension in NFL history this off-season. But Stafford is going to have to earn it this year. This will be his first season without Calvin Johnson, one of the best wide receivers of all time, so he’ll have to show what he can do without that weapon. However, just because he doesn’t have Calving Johnson doesn’t mean that Stafford doesn’t have weapons. Golden Tate and Marvin Jones have proven to be valuable wide receivers. Veteran wide receiver Anquan Boldin has had a fantastic career and should provide some depth to the receiving core. Theo Riddick is one of the best pass catching running backs in football and tight end Eric Ebron hopes to have a break out season this year. Stafford has all the tools necessary to succeed, he just has to go out and do it.