Mike Zimmer’s Vikings have spent ample time in recent years trying to pluck free agents from Cincinnati’s defense.

Zimmer was the Bengals defensive coordinator for six seasons before becoming Minnesota’s coach in January 2014. The Vikings soon took a look at defensive end Michael Johnson and then really targeted him last year, falling short both times.

The Vikings last year in free agency did land former Bengals cornerback Terence Newman. And they’ve also brought in over the past two years former Cincinnati defenders Chris Crocker and Taylor Mays, although neither ended up making the team.

Now, it might be time for another assault on the Bengals.

When teams Monday are first able to speak to representatives of free agents off other teams, a top Minnesota target is expected to be strong safety George Iloka, who has played four seasons with the Bengals, the first two under Zimmer. Iloka could be a perfect fit alongside Vikings star free safety Harrison Smith.

If the Vikings can’t land Iloka, Cincinnati’s other starting safety is also an impending free agent. Although Reggie Nelson most recently has been at free safety, he has played the strong spot before, and many observers believe he is just as comfortable there.

“George Iloka or Reggie Nelson would be a tremendous pairing with Harrison Smith,’’ said CBS and NFL Network analyst Solomon Wilcots, a former Vikings defensive back who lives in Cincinnati.

Iloka will be 26 next season while Nelson will be 33. Even though Nelson is coming off a Pro Bowl appearance while Iloka is not, age is one reason the website www.spotrac.com estimates Iloka’s market value as $5.6 million per season to $4.8 million for Nelson.

“(Iloka is) very smart,’’ Wilcots said. “He doesn’t give up big plays. He’s very disciplined and he’s got very good ball skills and good range. (Nelson) can play both safety spots. The way that Zim plays, they’re interchangeable. Reggie has always been versatile. He’s a very good range guy. I think he’s still playing some of his best ball of his career.’’

Speaking recently at the NFL scouting combine, Zimmer didn’t do much to conceal what a top Minnesota need in free agency could be.

“If Harrison Smith was paired with a guy that had some other qualities, we could allow Harrison to be more of an impactful player,’’ Zimmer said. “I think Harrison can be more impactful if he had the right kind of guy next to him.”

The Vikings on Saturday agreed to re-sign impending free agent Andrew Sendejo, last year’s starter at strong safety, to a four-year, $16 million contract. Sendejo is a special teams ace, and his agreeing to return doesn’t appear to impact Minnesota’s desire to beef up the safety spot.

Zimmer at the combine also noted he prefers bringing in free agents he once coached.

“When you’re messing around in free agency, I think the more you know a player the better chance you have of being correct,’’ Zimmer said. “So for me, a lot of it has been familiarity. Not only me knowing them, but them knowing me and how I am. I think that’s an important part of the process.’’

The Bengals have 14 free agents, including nine defenders who once played under Zimmer, so there are plenty to consider. Others who could be of interest include linebacker Vincent Rey, defensive end Wallace Gilberry and cornerback Leon Hall.

Then again, Minnesota general manager Rick Spielman has been relatively restrained in recent years in going after free agents. And with the Vikings preferring to build through the draft and coming off an NFC North title, that trend could continue.

“The theme and philosophy we’ve done is built through the draft, and all those draft picks now we’ve been able to accumulate, and with the coaching staff and how they develop young players, that’s starting to show up on the field,’’ Spielman said. “If you can continue to layer year in and year out and do a good job in the draft, I’d rather look to extend those guys in their second contracts then go out and do free agency. But there’s always a player here or there you may dabble in the free-agent market.”

The Vikings have about $25 million of salary-cap room. In addition to seeking a safety, key areas of need are the offensive line, depth at linebacker and finding a wide receiver, although it is a weak class at that position.

The offensive line was hampered in 2015 by season-ending injuries suffered in exhibition play by center John Sullivan and tackle Phil Loadholt. Running back Adrian Peterson did lead the NFL in rushing with 1,485 yards, but the Vikings gave up 45 sacks, 44 on Teddy Bridgewater.

“Teddy is going to get better every year, but that line in front of him has to get better,’’ Wilcots said.

The Vikings must make a decision by Wednesday, when the new league year begins and teams first can sign outside free agents, whether to keep tackle Matt Kalil, whose $11.096 million salary for 2016 becomes guaranteed then if he’s not released. It’s a tough decision whether to pay that much to Kalil, who has had plenty of struggles since making the Pro Bowl as a rookie in 2012, but it wouldn’t be a surprise if Minnesota gives him another chance to return to his previous form.

The Vikings have extended an offer to re-sign starting right guard Mike Harris on a two-year, $3.5 million deal that he is pondering. Harris entered the offseason as one of 17 impending Minnesota free agents. In addition to Sendejo, defensive tackle Kenrick Ellis also has agreed to re-sign, getting a one-year deal.

If the Vikings elect to make a big splash in free agency on the offensive line, one possibility could be Baltimore guard Kelechi Osemele, who also can play tackle and is one of the most highly rated prospects available. A less pricey option could be San Diego tackle Joe Barksdale.

In addition to picking up another offensive linemen, the Vikings also could help Bridgewater by signing another receiver. One possibly could be Miami’s Rishard Matthews, who has has shown steady improvement since being a seventh-round pick in 2012 and caught 43 passes for 662 yards in just 11 games last season.

Then again, the uninspiring class of free-agent receivers in one reason Minnesota is looking into bringing back Mike Wallace if he is willing to take a big pay cut from the $11.5 million he’s on the books for in 2016. The Vikings are more likely to look for a receiver in the draft.

The Vikings, who have taken Anthony Barr and Eric Kendricks in the past two drafts, also might prefer using the draft for a linebacker. There is some urgency since Chad Greenway is a free agent, and will play just one more season if he returns.

If the Vikings consider a linebacker in free agency, the versatile Rey could be a possibility. After all, he did play for the Bengals under Zimmer.