The D in Dallas doesn't stand for "defense"in 2020.While the Cowboys' offense has, as expected, been hitting on all cylinders, their defense has been on the side of a milk carton, Conor McDermott Jersey as in mi sing. That's a big reason for the team's 2-3 start to the season.Dallas was developing a mean defensive unit last year, but it hasfallen from top-10 status in 2019 to bottom of the barrel in 2020. New coordinator Mike Nolan has had his hands full with a group that is last in the league in scoring defense 36.0 points per game entering Monday's games, including the Cowboys' "Monday Night Football" matchup vs. the Cardinals (8:15 p.m. ET, ESPN). Dallas is on pace to shatterthefranchise record for most points allowed in a season.As always in football, there's not a single, cut-and-driedanswer for why the Cowboys' defense is historically bad. Here are three (and more) of the biggest reasons:MORE: Free-agent departuresIt starts with who isn't in Dallas. Offseason exits by several key players left the Cowboys needing to make a quick fix.They letByron Jones walk as a cap casualty; he took his talents to South Beach Mark Gastineau Jersey on a monster deal.Jones was tremendously underrated in Dallas; he was a key member of the secondary from the time he was drafted. Jones madeAll-Pro onceand hedisplayedversatility by playing free safety his first three seasons with the team and cornerback his last two. For years, the Cowboys were a revolving door at cornerback, and Jones shifting over therein 2018 helped to stabilize the position.Dallasalso lost their top pa s-rusher, Robert Quinn, who led the team with 11.5 sacks in 2019. He signed with the Bears in the offseason.The Cowboys have tried to plug those holes with Dontari Poe, Gerald McCoy, Everson Griffen and Ha Ha Clinton-Dix, but there havebeen . . .i sues: Aquad injury in training camp sidelined McCoy for the year, Clinton-Dix was released prior to the season and Poe and Griffen haveunderachieved.MORE: An underperforming D-lineDallas has some names you'd recognize, but they've been mi sing on Sundays.The Cowboys rank 20th in the league with 2.0sacks per game, downfrom 2.4in 2019. All things considered, this year's figureissolid, but here's some context: Dallas' D is built to get after the pa ser, and if it's not accruing sacks at an above-average rate, then the unit is in for bad results on gameday.DeMarcus Lawrence has been something of a Dan Feeney Jersey no-show with just a single sack. Everson Griffen hasn't exactly been an answer, either, accounting for 1.5sacks through the team's first five games.Dallas' inability to get consistent pre sure on the quarterback has left their secondary, which is le s than good, exposed, and that's a big reason why the Cowboys are near the bottom of the league in most major pa s defensecategories. Considering that they haveLawrence, Griffenand Aldon Smith rushing the pa ser, but still aren't getting after opposing QBs, that's not a tasty recipe for succe s. They're also re-adding Randy Gregory, coming back from suspension: the i sue? Gregory hasn Denzel Mims Jersey 't played since 2018.MORE: Coaching, scheme changesSeveral a sistantsweren't retained after Mike McCarthy tookover as head coach in the offseason. One of the results of that turnover was a scheme change for thedefense, which, in turn, has led to, well, what you've been seeing on the field every week.First, coordinator RodMarinelli Bart Scott Jersey was not retained; he woundup in Las Vegas with the Raiders as their new defensive line coach. In a surprise move, defensive backs coach/a sistant coordinator Kris Richard wasn't kept on, either;many expected himto be Dallas' next DC after he called plays for the unitin prior seasons. Richard was also a candidate for head coaching gigs in previous years.Now Nolan is coaching up the Dallas D, and he hasn't been a coordinator since 2014, when he was with the Falcons. Nolan's background caused some to believe he would alter the Cowboys'base defense from a 4-3 to a 3-4. Instead, Dallas has opted for multiple defensive fronts to make use of its roster pieces and to play a littleto Nolan's strengths.