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Training camp is well under way, which means that impressions have been made and position battles are heating up.

As Oakland looks to rebound from an 8-8 season that ended just shy of the playoffs, the Silver and Black are seeing an impressive performance from the team's defense this preseason.

The Raiders had brought in free agent Ron Bartell to anchor a redesigned secondary. After working with the first team defense during the offseason, Bartell suffered a hamstring injury a week before camp opened.

In his absence, second year CB DeMarcus Van Dyke has stepped up big time.

The Associated Press claims that Van Dyke has taken a physical approach while replacing Bartell at left corner (h/t Washington Post). The University of Miami standout broke up multiple passes from QB Carson Palmer on day one and recorded several more pass deflections on day two.

On day three, Van Dyke returned an interception for a touchdown and broke up a deep pass from Palmer.

Linebackers Rolando McClain and Travis Goethel have also made some big plays throughout training camp, including knock downs on both of Oakland's backup running backs, Taiwan Jones and Mike Goodson. As pass-rushing drills picked up over the weekend, the linebackers continued their strong outing.

McClain blew past Darren McFadden on a drill and also made a strong stop on Jones.

Big plays and pressure seem to be common motifs for the defense thus far, which has fared much better at camp than the offense. Although, cohesion is being seen in the offensive line as it adjusts to a zone blocking scheme and TE Brandon Myers was named the No. 1 tight end on the team's depth chart.

On Sunday, Bartell returned to practice, day one of a new three day transitional period that does not allow for full contact (via ESPN). Still, in limited action, he broke up a pass intended for WR Darrius Heyward-Bey.

Bartell, who had previously fractured his neck during the Rams opener last season, seems well-adjusted to injuries.

Via CBS Sports:

It's football so you're going to deal with some pain, but as long as I'm able to run without restriction I'm fine. I can deal with the pain. The issue is being able to run without restriction. I'm past that part of it. The pain can be managed and I feel pretty good.

Bartell is likely to retain his starting spot, as is veteran transfer Shawntae Spencer. Still, Van Dyke's impressive performance is worth noting as excitement builds around Oakland.

While the jury is still out on the offense, it is reassuring to know that the Raiders are likely to improve upon their 27th-ranked defense from a year ago.