There are rough offseasons. Then there are really rough offseasons. Then there’s the disaster that befell the San Francisco 49ers over the past several months. From the messy departure of head coach Jim Harbaugh to a number of stunning player retirements, it’s been a nasty stretch in San Fran, and the defense took their fair share of the hits.

Defensive Linemen

Granted, the retirement of defensive end Justin Smith wasn’t exactly a surprise, but it still left the 49ers with a sizable hole on the defensive line. The Niners looked to fill that hole with the addition of longtime division rival Darnell Dockett. Dockett remains a capable pro from an NFL perspective, but it’s been several years since the 34-year-old made an IDP impact.

No, if there’s IDP hay to be made on the d-line by the Bay in 2015 it will likely be by third-year pro Cornellius Carradine, who will be called upon to play a much bigger role this season. Carradine told Taylor Smith of the team’s website that he knows the pressure’s on.

“I have to continue getting comfortable in the system,” he said. “The more I get comfortable, the more I’m able to get out there and get experience, and the better it’s going to be for me helping the team by making plays.”

Could there be IDP upside here? Yes. But not enough to merit more than a late flier.

Linebackers

If the retirement of Smith was a hit, then the 49ers were absolutely jackhammered at linebacker. First Patrick Willis stunningly called it a career. Then 2014 rookie sensation Chris Borland dropped even more jaws by following suit.

That leaves an enormous hole inside for the 49ers, although the return of NaVorro Bowman from a scary knee injury and lost 2014 would surely help. According to James Brady of SB Nation, that return is one of the biggest keys for the 49ers in 2015.

“If Bowman is anywhere close to where he was at before his injuries,” Brady said, “then the 49ers are going to be a much better team than anybody outside of 49ers fans are guessing. Bowman is getting overlooked by just about everybody, and that bodes well for the 49ers. Let’s all hope he returns to form.”

It’s simple, really. A healthy Bowman could lead the NFL in tackles this year. But, Bowman is being drafted as though that health were a sure bet – it isn’t.

Outside Bowman, what was once the league’s best LB corps is wafer-thin. Even in a three-down role Michael Wilhoite offers little more than fantasy depth, and while pass-rusher Aldon Smith can be dominant while on the field, his myriad off-field issues make it hard to justify investing any real IDP draft capital in him.

Defensive Backs

The 49ers’ defensive MVP in 2014 wasn’t a linebacker at all. That honor went to safety Antoine Bethea, whose virtues were extolled by Tyler Emerick of the team’s website after a solid first season with the club.

“San Francisco’s MVP from a year ago,” Emerick said, “Bethea took over for Donte Whitner and didn’t miss a beat. The safety amassed 86 tackles, one sack, one forced fumble, 10 pass breakups and four interceptions, including one for a touchdown. The three-time Pro Bowler, now entering his second year in the Bay Area, gives the 49ers an assignment-sound, veteran presence in the secondary who isn’t afraid to come up and deliver the big hit.”

All those issues the Niners have in front of Bethea are actually a good thing where the veteran’s IDP prospects are concerned, and a second straight top-10 fantasy campaign in fantasy scoring isn’t out of the question.