PHOENIX -- The D-backs made a six-year, $120 million offer to free-agent right-hander Johnny Cueto earlier this month that was turned down, a baseball source told MLB.com on Sunday night.

The club has not confirmed the offer.

Starting pitching is the D-backs' biggest need this offseason, and it was believed that they had money to spend. How much they were willing to spend was a question mark, but the offer to Cueto may shine some light on it.

• Hot Stove Tracker

Cueto, 29, is regarded as one of the top-tier starting pitchers available on the market this offseason, along with David Price, Zack Greinke and Jordan Zimmermann, who is off the market after agreeing to a five-year, $110 million deal with the Tigers.

In 32 starts for the Reds and Royals last year, Cueto was 11-13 with a 3.44 ERA. He has made at least 30 starts in six of his eight big league seasons.

Video: MLB Now looks into the market value of Johnny Cueto

Cueto has the added bonus of not being tied to Draft-pick compensation, which means the D-backs would not forfeit the No. 13 pick in next year's Draft to sign him.

• 2016 Draft order

If the D-backs look to the next tier of free-agent pitchers, it includes the likes of Yovani Gallardo, Scott Kazmir, Wei-Yin Chen, John Lackey and Jeff Samardzija.

Of that group, signing Chen, Gallardo, Lackey and Samardzija would require the forfeiture of next year's Draft pick.

As it stands, the D-backs have Patrick Corbin set in next year's rotation, and there will be intense competition for the other spots with Rubby De La Rosa, Robbie Ray, Chase Anderson and Zack Godley among those in the mix, along with young prospects like Archie Bradley, Braden Shipley and Aaron Blair.

With that in mind, the D-backs had hoped to add one, or maybe even two, proven starters to the rotation.

Right-hander Kenta Maeda, who is expected to be posted by his Japanese team, is someone the D-backs have had an eye on as well.

"We've scouted him," D-backs general manager Dave Stewart said last week of Maeda. "So he would have to be in consideration. I would think that overall we feel it's going to help our team. He could be another option."