When you take a big-picture look at the work put in by the Winnipeg Blue Bombers over the past seven months, the magnitude of change the club is looking to institute in 2015 is somewhat staggering.

Head coach Mike O'Shea enters his second season at the helm of the digits and helmets, as does general manager Kyle Walters, in full charge of which players are donning them.

O'Shea hired veteran defensive coordinator Richie Hall to reshape a troubled defence, while retaining offensive coordinator Marcel Bellefeuille for continuity with a young quarterback stable, and Walters meticulously tweaked and steadily upgraded the roster throughout the offseason.

Frankly, on paper, the 2015 Bombers look barely a wisp of the unit that ran off 10 losses in their final 12 games of 2014.

What may effectively prove to be the biggest change in 2015 is also the biggest unknown in terms of what we'll see on the field and where new and returning players fit.

"It's not going to look like it did last year, that's for sure," said O'Shea of Richie Hall and an entirely new defensive staff. "If the word 'traditional' is the one that people are going to use, sure, it's going to look more like what people are used to. My concern is to just make sure it looks good and that it works. Those are words to describe it, and once again, we just want to make sure our defence is contributing to wins and playing tough football out there, and that they're able to on a game-in and game-out basis give us what we need to make sure we win games. That's basically the bottom line."

While the defensive backfield remains nearly entirely intact with returning starters Moe Leggett, Chris Randle, Demond Washington, Bruce Johnson and Matt Bucknor, gone are Johnny Sears, Ian Wild and Desia Dunn in the linebacking corps, as well as edge rusher Jason Vega.

With the need for new linebackers at the forefront, Walters targeted and landed a pair of Canadians in free agent Sam Hurl and supplemental draft pick Garrett Waggoner — with the GM investing his first-round pick in next year's draft to secure the rookie, banking on the third-generation CFLer to be worth a still-to-be-determined price.

The Blue Bombers' scouting department held open workouts across the United States throughout the offseason and, for a second year, a mini-camp in Florida to identify linebacker candidates among other positions.

"It's not just (about finding a middle linebacker)," said O'Shea. "Florida is about bringing depth and competition to training camp at all the positions. It's not about finding one particular guy. We're pretty excited about the signing of Sam Hurl, but we also know that we've got to fill out our roster and create that environment that we're looking to create."

"What's going to be constant for us is to always make sure that we have depth and we have competition at as many spots as possible," added the head coach. "And that's a good thing, and I believe as professional athletes, these guys, they enjoy that. They don't want to get to a point where they feel they've made it — they like the idea of competing on a daily basis, and when they win a job it means something special to them."

In an astute move, Kyle Walters signed Canadian defensive end Jamaal Westerman following six seasons in the NFL. If the club chooses to start a Canadian on the D-line, it'll surely be the 260-pound 30-year-old.

"We just need overall depth, everywhere," said Walters while taking a moment away from assessing the 2015 draft class in Toronto at the CFL Combine in March. "We're still a long way away from getting where I feel we need to be Canadian-depth-wise. The offensive line is always a concern — you always need to address those guys, and you always need to get young guys in and develop. Receivers, we could use some more depth."

And with the second and 11th-overall picks, Walters indeed addressed those areas by selecting hard-nosed interior lineman Sukh Chung, and 6-foot-5 receiver Addison Richards, who was a pass-catching machine in his final year at the University of Regina.

After allowing a franchise-record 71 sacks last season, the most critical offensive upgrades came via free agency when Walters locked up All-Star blindside tackle Stanley Bryant, veteran centre Dom Picard and tackle Marc Dile. Bryant replaces veteran Glenn January, who was not re-signed, and Picard supplants Steve Morley who was released last month.

The club surely hopes slotback Clarence Denmark can duplicate his 1,000-yard 2014 campaign, Nick Moore can stay healthy enough to approach similar numbers and tailback Paris Cotton will be pushed by speedy newcomers Bradley Randle and Carlos Anderson, while bigger bodies, Da'Rel Scott and Cam Marshall, can add power to a more balanced run attack.

And then there's quarterback Drew Willy, of course. His 3,769 passing yards in his first season as a pro starter have Walters and company confident in his ability to steer the ship — they extended his contract through 2017 — but the 28-year-old's ratio of 14 interceptions to just 16 touchdowns last season have all eyes locked on Marcel Bellefeuille and his ability to take full advantage of revamped protection and turn the tides for his franchise quarterback and the Bombers' offensive attack.

Now the actual work begins in earnest as the Blue and Gold set out on three days of "rookie camp" on Wednesday, May 27 with first-year CFLers and quarterbacks hitting the turf, while main training camp runs Sunday, May 31 up until their final preseason game against Hamilton on June 19.