It's been a year since the last prospects series, but here we are again. Every weight class will be touched, from heavyweight to flyweight and everything in between. 

The heavyweight division is one of the smallest divisions in terms of quantity and depth. Of the hundreds of fighters on the UFC roster, the heavyweight division has just 28 fighters.

The division is currently ruled by two-time champion Cain Velasquez, who defends his title at UFC 160 against Antonio "Big Foot" Silva. Other contenders in the division include Junior dos Santos and Daniel Cormier.

Here are five heavyweight prospects that the UFC should sign to help add depth to the division. 

Note: Here is last year's top-five list. None of the five included were signed.

Derrick Lewis

Record: 9-2 (1 NC)

Last Fight: Knockout win vs. Ricky Shivers

Known as "The Black Beast," Derrick Lewis is a stone-cold killer. The man is powerful, athletic and quick—a combination of qualities that is rarely seen in the heavyweight division all at once.

He has fists of pure steel. When he hits you in the head, it is likely that you will be going to sleep.

In nine professional wins, Lewis has knocked out eight men, including Bellator veteran Ryan Martinez, Jared Rosholt and Ricky Shivers. This is a testament to his boxing and power. 

Lewis has fought for respectable MMA organizations such as Legacy Fighting Championships and Resurrection Fighting Alliance. He is definitely ready to make the jump to the UFC.  

Damian Grabowski

Record: 16-1

Last Fight: Unanimous decision victory vs. Dave Huckaba

It's hard to call a 17-fight veteran a prospect, especially considering the level of competition Damian Grabowski has faced. However, it's time for the well-rounded Polish fighter to make the jump to the UFC.

The Bellator veteran has long been considered one of the best European heavyweights around. He owns 14 finishes to his name (nine submissions, five knockouts), including wins over Eddie Sanchez, Joaquim Ferreira and Dion Staring.

Perhaps the money in Poland is keeping him there, but one has to think if he fought for Bellator three times that the UFC could offer him more. He would be especially valuable seeing that the UFC is expanding into Europe.

Grabowski currently is slated to meet fellow European prospect Stav Economou on April 27 in Poland. Should he win, the UFC may have to pursue him. 

Maro Perak

Record: 22-3-1

Last Fight: Split decision win vs. Travis Wiuff 

Speaking of impressive European heavyweights, Croatia's Maro Perak has carved out a pretty impressive record of his own overseas.

With 26 fights under his belt, Perak brags a high finishing rate in wins (82 percent), including 11 knockouts. He is a nasty striker that makes up for his lack of size with power, quickness and strength.

His resume includes wins over Bob Sapp, Travis Wiuff and Miodrag Petkovic (twice). His counter-wrestling could use some work, but where better to test his all-around arsenal than the best MMA promotion in the world?

I'm sure we would see a knockout or two in his tenure.

Smealinho Rama

Record: 6-0

Last Fight: Knockout victory vs. Mike Hackert

Smealinho Rama is Canada's best heavyweight, hands down. That is impressive considering he has just six professional fights under his belt.

All six of Rama's wins have been finishes, with three happening by knockout and three by submission. The Maximum Fighting Championship veteran owns finishes against Mike Hackert, Ryan Fortin and Lee Mein—an impressive hitlist. 

At just 20 years old, Rama has a very bright future in MMA. His next bout is on May 10 when he meets experienced brawler Chris Barnett.  

Satoshi Ishii

Record: 7-2-1

Last Fight: Submission victory vs. Kerry Schall

Satoshi Ishii is a Japanese judoka that has turned into quite the mixed martial artist. The 26-year-old has been on a tear since his knockout loss to Fedor Emelianenko last year.

Four of Ishii's wins have come via submission, with all four coming via armlock (two armbars, two kimuras). His list of victories includes wins over former UFC champion Tim Sylvia, UFC veteran Sean McCorkle and kickboxing ace Jerome Le Banner.

His top-level judo in addition to his savvy grappling and solid ground-and-pound would make him a potential top guy with the company.