The Chicago Bulls' defense took a step back last year and was one of the league's worst the second half of this season. The absence of Joakim Noah played a factor in that, as Pau Gasol got worse and worse on that end as the year went on and the other bigs weren't capable of anchoring a defense.

The Bulls are now looking at the likely exits of both Noah and Gasol, and they're going to need somebody to fill the void at center (no, Cristiano Felicio isn't the answer, although he can be a valuable piece!) if both players exit. Ideally, that player is a youngish, defensive-minded athlete who can protect the rim and adequately guard pick-and-rolls. That kind of player could pair with the more offensive-minded Nikola Mirotic or Bobby Portis and not make me feel woeful about the Bulls' defensive chances.

There are a couple of players on the market who fit the bill here that I'd like to discuss, although I fear at least one of them has priced his way out of Chicago's range: Bismack Biyombo and Ian Mahinmi.

Biyombo

I wrote a bit more on Biyombo over at the SBN mothership, but the short version is he went from a Hornets cast-off to a postseason breakout star after Jonas Valanciunas went down with an ankle injury for the Raptors.

Scouts raved about Biyombo's potential coming into the league thanks to his athleticism and freakish wingspan, but his offensive game was incredibly raw and still isn't that developed, although he has made modest improvements.

But Biyombo, who's still only 23 years old, excelled this season by playing to his strengths, which are defense and rebounding. He was a terror in the middle for the Raptors all year, anchoring the team's second unit throughout the regular season and then doing the same as a starter in the playoffs, although things came back down to earth in Games 5 and 6 against Cleveland.

But Biyombo had several monstrous postseason performances, including Game 7 against the Heat and both Games 3 and 4 of the Eastern Conference Finals. He grabbed a franchise-record 26 boards in Game 3 and had several highlight-reel swats in the series, plus a near one:

Biyombo was called for a foul on that second one, but I'm still mesmerized by how he basically went from the opposite elbow to the other side of the rim and nearly packed LeBron freaking James on an alley-oop. That kind of rim protection was the norm all season for Biyombo, who was one of the league's best in both the regular season and playoffs, per SportVU.

The problem, of course, is that this playoff run has ballooned Biyombo's salary this summer. He's talked about taking a hometown discount with the Raptors, but there are also reports of him getting offers in the range of $17 million annually, per Sporting News' Sean Deveney.

As much as I like what Biyombo would bring to the Bulls, that's a tough price to pay given his limitations, even with the rising cap. Chicago could certainly have the cap space to make that kind of offer if it so chooses, but they'd correct to be hesitant about doing so. Even so, they should definitely at least look into it.

Mahinmi

Mahinmi isn't that young as he'll be 30 at the start of next season, but he doesn't have nearly the miles on his body as a guy like Noah or even Taj Gibson does. This was his first season as a full-time starter, and he acquitted himself quite nicely.

The Pacers may have been a chore to watch offensively, but they again put forth an excellent defensive campaign with Mahinmi taking the place of the departed Roy Hibbert. Indiana ranked third in the league by allowing just over 100 points per 100 possessions, and that mark was at 98 points per 100 possessions with Mahinmi on the court, per NBA.com.

Mahinmi is just shy of seven feet and has plus length and athleticism, and while he was strong defensively all season, he really terrorized the Raptors in their first-round series. Toronto managed just 91 points per 100 possessions with Mahinmi on the floor, and they shot under 35 percent at the rim against him.

Overall, Mahinmi averaged a solid nine points and seven rebounds in 25 minutes per game on the year, and he significantly improved his true shooting percentage (51.6 percent to 60.3 percent) and PER (10.84 to 16.66). His assist rate also saw a nice little bump while his turnover rate went down.

Like Biyombo, Mahinmi doesn't do much outside of the restricted area and doesn't have the best hands, but he was an excellent finisher at the basket, converting on over 68 percent of his attempts down there.

Mahinmi should be cheaper than Biyombo given the age differential and fact that Biyombo probably hasn't yet hit his ceiling, so this is a more realistic option for Chicago. Given the cap spike, maybe something in the $10-12M range annually? Maybe I'm underestimating it because big men get paid, but that seems more than fair.

Some may feel like Mahinmi is a band-aid and doesn't move the needle, and I get that sentiment. But if the Bulls are going to try to be competitive here in the next few years, he could help.

Other options

There are other center options available, but I'm not crazy about any of them. Hassan Whiteside would be nice in theory, but he almost certainly isn't coming. Dwight Howard is a big fat no. Festus Ezeli is intriguing, but he's got a history of knee issues and has had problems staying on the court in the playoffs for Golden State. Plus, he's a restricted free agent. Timofey Mozgov has been utter trash with the Cavaliers this year and is out of the rotation. And as much as I love my alma mater (well, I kind of hate their basketball program now), Meyers Leonard isn't doing it for me. And no, neither is Roy Hibbert. Then we're getting down to guys like Tyler Zeller, Miles Plumlee and Cole Aldrich, who I guess could be okay if they could be had at great value.

So assuming Whiteside is out, I'm looking at Biyombo and Mahinmi first, while possibly kicking the tires on Ezeli. If that strikes out, then you go down to those lower tier of players and hope a guy signs for cheap while outplaying his contract, kind of like what happened in Portland this season. Bringing back Noah may still be an option as well despite certain reports, but only on the right contract.