Pictured: Anderson Silva (Left) -- Dave Mandel/Sherdog.com

Strikeforce's April 17 card in Nashville didn't quite deliver the excitement that many had hoped. However, it did introduce a new entrant to this list while striking down another. Jake Shields has remained unbeaten for five years and counting. Over 14 victories, he has beaten the likes of Yushin Okami Robbie Lawler , Jason "Mayhem" Miller and now Dan Henderson . Shields' rousing upset victory over Henderson to retain the Strikeforce middleweight title solidified him as one of the sport's elite, creating a serious question as to whether the Cesar Gracie standout will remain with the San Jose-based promotion or if the near future will see him in the Octagon.Meanwhile, in his stateside debut, Shinya Aoki was unable to dazzle the American audience the way that he'd done for crowds on the other side of the Pacific. The Dream lightweight champion was soundly dominated from bell to bell by Gilbert Melendez , who easily won every round against the typically slick grappler.The rush of activity for these pound-for-pounders is not over: Saturday night in Sacramento, both Jose Aldo and Mike Thomas Brown will be in action at WEC 48, looking to further stake their places in the 145-pound division and perhaps move toward a rematch in the future.Nearly two weeks removed and with Strikeforce's in-cage brawl in Nashville now being MMA's primary flak magnet, Silva has managed to escape further criticism stemming from his UFC 112 performance against Demian Maia . We also know what's next for "The Spider," as Dana White was quick to announce that the middleweight kingpin would be back in action in August, defending his title against trashtalking political candidate Chael Sonnen . Though it is a far cry from the fight with Georges St. Pierre that was teased prior to the Maia debacle, it is a bout that will assuredly draw its fair share of hype courtesy of Sonnen's gift of gab.It is the kind of nitpicking that can only result when a fighter is as dominant as St. Pierre. After another complete performance at UFC 111, with his UFC welterweight title up for grabs, one would anticipate that GSP’s crushing of Dan Hardy would have impressed onlookers. Instead, in spite of particularly vicious armbar and kimura attempts that contorted the arm of “The Outlaw,” MMA’s welterweight king has been disparaged as a safety-first top-position wrestler who is content to do just enough to win fights. Critiques aside, the constant stream of elite challengers will not stop for St. Pierre, whether they come from the ever-deep 170-pound division or courtesy of a move to 185 pounds.Emelianenko was supposed to embark on his next conquest for Strikeforce in April, this after he had wiped out Brett Rogers in thrilling fashion in the promotion’s November CBS debut. However, a contract impasse between Strikeforce and M-1, Emelianenko’s representation, put the breaks on his appearance. Now his next bout looks more likely for June or July. In some ways, the delay may be a blessing in disguise. It will not buy Strikeforce a world of time, but if Emelianenko had fought and knocked off Fabricio Werdum as anticipated, it would have left the Russian with one last obvious foil -- Alistair Overeem -- as we entered the summer. Now the obvious end of Strikeforce’s short heavyweight gallery is further off.After ripping through Thiago Silva and Rashad Evans in consecutive bouts in 2009, Machida had already ignited complaints about the inability of other light heavyweights to challenge him before he even defended the UFC title. His October bout with Mauricio “Shogun” Rua vividly showed once again the folly of proclaiming any MMA fighter unbeatable, as Machida’s unanimous decision victory became the most debated and unpopular decision of the year. With the Rua rematch slated for May 8 at UFC 113 and a growing number of highly gifted 205-pound prospects in MMA, Machida’s road to dominating the light heavyweight division has quickly become a much taller task than previously anticipated.Since his World Extreme Cagefighting debut in June 2008, Aldo is 6-0 with six stoppages, including four in 2009 alone. It is little wonder that the hottest thing out of the Amazon jungle was Sherdog.com’s “Fighter of the Year” for 2009. However, Aldo’s brilliant campaign last year leads to a harder road from here on out. Aldo will be tasked with defending his title against the top featherweight challengers the WEC has to offer, fight in and fight out. It starts with former champion Urijah Faber at WEC 48 on April 24 in front of a highly partisan Sacramento, Calif., crowd that will want him to lose and lose badly. If Aldo is truly set to become MMA’s first featherweight superstar, we will find out shortly.With a straightforward and prosaic fighting style, Fitch is not as close to another crack at the UFC welterweight title as he would like to be. However, the former Purdue University wrestling captain still sports a staggering 12-1 record in the UFC, and in one of MMA’s greatest divisions. Even if his dream fight is a rematch with Georges St. Pierre , the high-stakes bout for Fitch in the interim will be his rematch with Thiago Alves . After two previous delays, a fight between the former title challengers is slated for UFC 115 in Vancouver, British Columbia, Canada, on June 12, with the winner locking up second fiddle status in the ever-deep welterweight division.The world has fallen so deeply in love with Jose Aldo that Brown’s featherweight reign seems like five years ago, not five months ago. While it will be the man Brown conquered twice in his biggest wins, Urijah Faber , who next challenges Aldo for the 145-pound throne, Brown will find a home on the same WEC 48 card. In order to rise back up the ladder for a chance to regain the WEC crown, Brown will have to deal with fellow UFC veteran Manny Gamburyan , who owns a 2-0 mark since dropping to the more physically appropriate 145-pound division.At UFC 112 in Abu Dhabi, United Arab Emirates, Edgar scored the most significant win of 2010 so far by dethroning lightweight kingpin B.J. Penn and taking the UFC 155-pound title. Though it was not exactly a popular decision, Edgar took all three judges’ scorecards on the back of his aggressive combination punching and stellar movement. However, the new surprise champion will have to replicate his feat in order to earn unanimous consideration as the sport's top lightweight, as the wheels are in motion for an August rematch between he and Penn in Boston.From one controversy to another, Penn lost his UFC lightweight title and MMA's 155-pound mantle on April 12 with his shocking upset to Frankie Edgar . While debate still rages over the bout's outcome, Penn has started his book tour to promote his eye-opening biography. The book has drawn the particular ire of UFC boss Dana White for its anecdotes of the Hilo native's past dealings with the company. Brouhahas notwithstanding, "The Prodigy" will get his chance for redemption and to regain top status at 155 pounds in August, when he figures to rematch Edgar at UFC 118 in Boston.There was a time just a few short years ago when Shields was reviled for being one of MMA's most loathsome fighters to watch. However, over the last five years, the Cesar Gracie product has transformed from a drab, peripheral contender to one of the sport's elite. With his dominant April 17 upset over Dan Henderson , the Strikeforce middleweight champion now boasts a 14-bout winning streak and top-five credentials in two separate divisions. The serious question surrounding Shields now is simply whether he will remain a Strikeforce commodity or if his future lies in the Octagon against a deeper roster of competition.