The 49ers placed big-money bets Monday that free safety Jimmie Ward will stay healthy and defensive lineman Arik Armstead will remain a sack machine.

And, sandwiched between those moves, they traded an All-Pro two-time team captain who was a sure thing when it came to availability and production.

Talk about risky business.

Before diving into the 49ers’ decisions to sign Ward (three years, $28.5 million) and Armstead (five years, $85 million) to backloaded contract extensions and trade defensive tackle DeForest Buckner to the Colts for the No.13 pick in the NFL draft, let’s say this: Dealing Buckner gave them needed salary-cap space and draft capital, which could help them maintain long-term success.

Now, about that risky stuff.

Ward, 28, has been so injury prone throughout his six-year career that fans howled a year ago when the 49ers brought back the 2014 first-round pick on a relatively modest one-year contract. To review: Ward has broken his foot, collarbone (twice), forearm (twice) and finger, causing him to miss 32 of 96 games and end four seasons on injured reserve.

He earned his three-year extension after making 16 straight starts (including playoffs) last season, marking the second time he has played in more than 11 games.

Still, his largely healthy and stellar season came with an asterisk. He broke his collarbone during an offseason practice and missed the first three games because of a broken finger.

Ward, when on the field, has resembled a first-round pick.

But the same can’t be said for Armstead, 26, the No. 17 selection in 2015 who had nine sacks and missed 18 games to injury in his first four seasons.

Armstead broke out in 2019, a contract year, with a team-high 10 sacks while remaining an excellent run defender. Some of his uptick in production had to do with his massively upgraded supporting cast: Armstead benefited from the additions of edge rushers Nick Bosa and Dee Ford and Buckner continued to attract double-teams inside.

Now, Armstead won’t benefit from Buckner’s presence and the 49ers’ defensive line, a big reason for last season’s run to the Super Bowl, almost certainly won’t be as ferocious in 2020.

Buckner has ranked among the NFL’s top five defensive tackles in sacks, quarterback hits, tackles, snaps and starts since he entered the league. He started 66 of 67 games, including playoffs, and played a major role in setting a tone for a locker room that was widely celebrated for its chemistry and selflessness.

Last season, Buckner won the Bill Walsh Award, which is voted on by coaches and is, in effect, the team MVP. In 2018, he won the Len Eshmont Award, the team’s most prestigious honor, which is voted on by players and recognizes courage and inspiration.

Buckner, who turned 26 on Tuesday, was a franchise pillar in his prime who will merit Hall of Fame consideration if he remains on his current trajectory.

So why trade a model player and teammate?

The 49ers couldn’t keep every stalwart from their Super Bowl team because of finances, and Buckner, who agreed to a four-year, $84 million contract with the Colts, had premium trade value.

This is how good teams often sustain success: By making unsentimental decisions that can provide long-term dividends.

With the No. 13 pick, the 49ers could draft Buckner’s replacement, who would sign a rookie contract for a fraction of his cost. Last year’s No. 13 pick, Miami defensive tackle Christian Wilkins, signed a four-year, $15.5 million contract.

Of course, the 49ers also could use the selection to select a much-needed wide receiver in a draft that’s historically stocked at the position. Or they could trade the pick for more selections in a draft in which they don’t have a second-, third- or fourth-round pick.

The point: Trading Buckner gives them options beyond the ability to spend more in free agency this week with his $12.378 million salary for 2020 off the books.

But Buckner was a guaranteed standout and the 49ers now have to make the right moves for their decision to pay off.

For example, there’s no guarantee the No. 13 pick, if they keep it, will come close to matching Buckner’s value. Consider: Of the past 30 players picked at that spot, five have earned All-Pro honors.

So, yes, Monday’s moves invited plenty of questions.

Can Ward stay upright? Can Armstead keep taking down QBs? And can the 49ers maximize the money and draft capital they received in the trade?

What’s known is this: Dealing Buckner didn’t make them better.

At least not immediately.

Eric Branch covers the 49ers for The San Francisco Chronicle. Email: ebranch@sfchronicle.com Twitter: @Eric_Branch