For years, the Vikings have prided themselves on building talent through the draft, and General Manager Rick Spielman was noted for making several moves to build up roster depth through draft-day trades.

But with the offseason departures of Chad Greenway, Adrian Peterson, Matt Asiata, Audie Cole, Rhett Ellison, Matt Kalil and Jeff Locke, the Vikings are looking at a slight rebuild of that depth, especially on offense.

The Vikings will be looking to see who from this weekend's crop of draft picks, and rookie free agents, will be able to help them this season.

In looking at the current depth chart, which obviously could change before the season opens, the team has drafted only two players considered locks for the first-team offense: wide receiver Stefon Diggs (fifth round in 2015) and tight end Kyle Rudolph (second round in 2011).

If quarterback Teddy Bridgewater were to work his way back from injury, or if receiver Laquon Treadwell can work his way into steady playing time after a nearly invisible rookie season, they would be the two lone first-round draft picks on the offensive side of the ball.

The offensive line, which for years had several Vikings picks in the starting unit such as Phil Loadholt, Matt Kalil and John Sullivan, has no homegrown selections projected to start. That could change if someone such as holdovers T.J. Clemmings and Willie Beavers or 2017 picks Pat Elflein and Danny Isidora earn starting spots. Elflein is a third-round pick from Ohio State who won the Rimington Award for being the nation's best center last year. Fifth-round pick Isidora is a guard from Miami who was a three-year starter.

The Vikings signed two free agents this offseason who figure to be starters in Riley Reiff, a 2012 first-round pick of the Lions, and Mike Remmers, a former undrafted free agent who previously played for the Vikings but made his name with the Panthers.

Alex Boone was a free-agent signing last year from San Francisco, and he also began his career as an undrafted free agent. Joe Berger, whose could play either guard or center, began his career as a sixth-round pick with Carolina before joining the Vikings in 2011. And Jeremiah Sirles, who has a chance to start at tackle, is another undrafted free agent who started his career with the Chargers.

When it comes to the offensive skill positions, second-round pick Dalvin Cook joins a running back group that includes former third-round pick Jerick McKinnon. Both figure to back up free-agent signee Latavius Murray, a sixth-round pick by the Raiders in 2013.

At receiver, Diggs will be one of the stars of the Vikings offense. He was a fifth-round pick in 2015, the 146th player taken overall, but looks like the second- or third-best receiver to come out of that class. The Vikings also have gotten a lot out of Adam Thielen, who joined them as an undrafted free agent out of Minnesota State Mankato in 2013 and blossomed last season.

Then there is quarterback Sam Bradford, the former No. 1 overall selection by the Rams, and the player the Vikings acquired from the Eagles for this year's first-round selection.

If you look at the Vikings offense, it's clear Spielman and coach Mike Zimmer are going to try and build up that side of the ball with draft picks, because they simply can't continue to rely on making multiple free agent moves each season.

Defense shows the way

On the other side of the ball, the Vikings have the blueprint for how to build depth and stardom through the draft, as they built a defense that ranked as one of the best in the NFL last season.

The Vikings feature seven players on the first-team defense who were drafted by them, with the caveat that no one is sure what to expect from Sharrif Floyd, who is dealing with nerve damage to his knee.

On the defensive line, Brian Robison was a fourth-round pick in 2007, Floyd was a first-rounder in 2013 and Everson Griffen was a fourth-rounder in 2010. Linval Joseph was a second-round pick of the Giants in 2010 before signing here in 2014, and this year the Vikings added another free agent in Datone Jones, a Packers first-round pick in 2013.

The linebacking corps features two of the Vikings' best picks in recent memory in 2014 first-rounder Anthony Barr and 2015 second-rounder Eric Kendricks. With the retirement of Greenway, the Vikings made one big move this offseason in that group by signing Emmanuel Lamur, an undrafted free agent from 2012 who played for Zimmer with the Bengals.

In the secondary, the Vikings' stars are both first-round picks, safety Harrison Smith (2012) and cornerback Xavier Rhodes (2013). The team also has gotten great production from veteran cornerback Terence Newman, a fifth-round pick by the Cowboys way back in 2003, and safety Andrew Sendejo, an undrafted free agent with little NFL experience who has started 40 games for the Vikings since signing in 2011.

Yes, if you want any indication of how difficult and confusing the draft can be, consider this: If their current depth chart were to hold, the Vikings would have four former first-round draft picks starting on the defensive side of the ball, and four former undrafted rookie free agents on the offensive side.

JOTTINGS

• Vikings quarterback Sam Bradford said this past week that he is looking forward to having a full offseason with his teammates. "Just to be here this offseason, to be able to go through the program, go through the meetings, the installs, really sit down and learn this offense and what we're trying to do," he said. "It's a much better situation than showing up here however many days, eight or nine days before the first game last year and trying to learn everything on the fly."

• Vikings Vice President Lester Bagley said the team has taken some of the pressure off its construction schedule for its Eagan facility because of all the planning around next year's Super Bowl. "We decided rather than put pressure on the construction in Eagan, which is roughly going to be finished at the same time, the completion date in Eagan is March 1 and the Super Bowl is February 4, three weeks prior," Bagley said. "Eagan will not be officially opened. It could be close to completed by the Super Bowl, but the Eagan project is one that's coming fast."

• Timberwolves coach Tom Thibodeau said guard Zach LaVine's rehabilitation from a torn knee ligament is progressing. "He has been coming along well, his approach has been terrific," Thibodeau said. "As you know, he's an upbeat guy, but he has put a lot of work into the rehab. And not only the recovery with the ACL, but the things he can do. He's controlling that and doing a lot of weightlifting and he's able to shoot the ball and work on ballhandling and passing drills without a lot of movement."

• Former North Stars player Brian Lawton, who does great analyst work for the NHL Network, was asked why he picked the Blues to beat the Wild in the playoffs, and wasn't surprised when it happened. "Obviously I felt like the St. Louis Blues were a completely different team after Mike Yeo took over," Lawton said. "They just changed some things defensively that I thought really helped them and played to their group. They also found their identity."

Sid Hartman can be heard Monday and Friday on WCCO AM-830 at 8:40 a.m. and Sundays at 9:30 a.m. E-mail: shartman@startribune.com