When Nate Diaz was interviewed in the Octagon following his tour-de-force win over Jim Miller at last weekend's UFC on FOX 3 card in New Jersey, he left no doubt who he considered the number-one lightweight in the world: Strikeforce champion Gilbert Melendez.

You'd expect him to say this, of course, since the two are training partners. But figuring out where Melendez should rank, exactly, isn't so cut and dried.

With six straight wins, the 20-2 Melendez has the second-longest current win streak of any top-10 lightweight, trailing only unbeaten Bellator champ Michael Chandler (10). During that run, "El Nino" avenged his only two career losses, to Josh Thomson and Mitsuhiro Ishida.

But can Strikeforce provide the quality of competition necessary to make a case for Melendez as No. 1?

Strikeforce has put together Melendez and Thomson in San Jose on May 19 in what might be the least-anticipated trilogy fight of recent times.

If Melendez wins that matchup, as most expect, then what? Strikeforce's 155-pound division is running pretty thin these days.

As is its stable of bankable headline talent, with Nick Diaz, Jake Shields and Dan Henderson all back in the UFC; Cristiane "Cyborg" Santos suspended due to steroids, and the seemingly interminable heavyweight tournament finally winding down next week.

Showtime isn't about to let go of one of the few remaining television draws it has at its disposal, which means Melendez might fritter away his prime against less-than-elite competition.

Diaz could very well be correct in calling Melendez the best in the world. But as long as Melendez is in Strikeforce, we'll never find out.

(Note: The fighter's rankings the last time we ranked the lightweights are in parentheses.)

1. Benson Henderson (4) If you want to find something to nitpick about the champion, he hasn't finished an opponent since submitting Donald Cerrone back in 2010. Beyond that, there's not much to criticize about the current king of the hill.

2. Gilbert Melendez (2) It's probably not fair that Melendez is being judged for a situation that's out of his control. But at the same time, the situation puts more pressure on the champ to look impressive in each outing, beginning with his bout against Thomson.

3. Frankie Edgar (1) When undersized fighters who take a lot of damage hit their career turning point, it happens in the blink of an eye. I'm not saying Edgar is there yet, but he's taken beatings in his past several fights and he's only won one of his past three.

4. Nate Diaz (10) The hottest fighter at 155 pounds not wearing major-promotion gold at the moment. Will a long wait for the winner of the Henderson-Edgar rematch serve to cool him off.

5. Gray Maynard (3) Yes, I'm aware Maynard beat Diaz on a split decision two-and-a-half years ago and that I'm ranking Diaz ahead of Maynard anyway. But Maynard hasn't won a fight in 21 months, while Diaz has blazed his way through the weight class. The good news for "The Bully" is that he can rectify this next month when he meets the next fighter on the list.

6, Clay Guida (5) The only loss on his record in this decade was his Fight of the Year-candidate decision against Ben Henderson in November. But he's hardly the only one to lose to Bendo, and a win over Maynard would put him right back into the Top 5.

7. Anthony Pettis (6) Still nothing on the docket for "Showtime," who has won seven of his past eight fights. Highly unlikely it will be a UFC title shot, though.

8. Jim Miller (7) Miller had a strong run in winning seven consecutive UFC fights form 2009-11. But he's also 0-4 against guys ranked ahead of him on this list. He will need a strong win in his next outing to stay ranked.

9. Michael Chandler (NR) The unbeaten Bellator champ KOd Japanese legend Akihiro Gono directly into retirement.

10. Eddie Alvarez (NR) The Philly phenom rebounded from his Bellator title loss to Chandler with a convincing TKO of Shinya Aoki, avenging a previous loss.

Want more? Then check out USA TODAY/SB Nation's Consensus Rankings for each weight class from bantamweight to heavyweight.