The Raiders defense let the team down quite a few times last season, but showed vast improvement throughout the course of 16 games.  Oakland drafted a key piece to their defensive unit with their first selection in the 2014 draft, Khalil Mack who burst onto the scene making an immediate impact.  They have a nice combination of young players as well as veterans who know what it takes to win in this league.

Here’s a look at how the Raiders defensive unit shapes up for 2015.

Looking at the defensive line, the top players are Mack, Sio Moore, and the vet Justin Tuck.  Tuck was signed last offseason, but didn’t produce as much as expected; the Raiders expect more from him in the pass rush this season.  Mack’s numbers weren’t mind boggling, but his display on the field was impressive for a rookie season.  The youngster has been working hard this offseason adding 18 pounds of added muscle to become even more intimidating on the field as he looks to add to his season sack total.  Last year, Mack had four sacks, but hard work pays off as he seeks to be a force to be reckoned with in 2015 alongside Moore.  

The two formed quite the duo last year, and will look to build off that chemistry for years to come.  Moore had three sacks last season, but has proven to be a motivator on the roster.  He can always be found firing up Raider Nation and his teammates on critical third down plays.  

Justin Ellis and Dan Williams hope to bring a lot to this defensive line this season and add to a pass rush threat.  Going into the offseason, the pass rush was a concern, but was not addressed by the Raiders as they didn’t add an established defensive end.  

Last year, the Raiders only had seven sacks from their defensive ends, the fewest in the NFL.  Looking ahead to this season, the defensive line looks to improve against the run as they were ranked 22nd in that category last season.  The D-line should be decent this year, but isn’t considered a top unit.

The Raiders secondary is questionable.  They struggled last season, but are led by Charles Woodson who like fine wine seems to get better with age.  

DJ Hayden was the Raiders first round pick in 2012, but has yet to live up to the hype while being hindered by injuries.  The corner has yet to play a full season, but did show flashes of talent last season.  

In 2014 the Raiders defense was ranked 21st overall allowing 5,721 yards and 452 points.  When it comes to the pass, the Raiders were ranked 16th defensively allowing 3,810 yards.  

Defense is an important piece to the best teams in the league.  An offense can put up as many points as possible, but it's up to the defense to maintain a lead and keep the opposition out of the endzone.  

Oakland’s defense is a work in progress, but they have some key pieces on their roster as they continue to rebuild.