Ruh-roh.

Anthony Johnson was all set to welcome perennial middleweight contender Nate Marquart to the 170-pound division this coming June 26 at UFC on Versus 4 in Pittsburgh, Pennsylvania; however, an injury has forced him off the card.

Stepping in to replace him will be Rick Story, who gets that big fight he was looking for without having to take on Jon Fitch.

The promotion brought word of the switch via its Twitter account.

Story has accepted this bout less than a week removed from his three-round war against Thiago Alves at the UFC 130 event on May 28. He absorbed a ton of punishment but outlasted "Pitbull" on his way to a unanimous decision win.

It was the sixth in a row for "Horror" who has been campaigning for a shot at the welterweight title. He's steadily working his way up the ladder, picking off contenders as he goes.

Next up: a divisional newcomer with a stellar track record.

After his dominant decision win over Dan Miller at UFC 128: "Shogun vs. Jones" last month, muscle-bound Marquardt shocked just about everyone when he made an off-the-cuff remark that he was toying with the idea of dropping a weight class.

He was apparently serious, regardless of the fact that his long-time training partner, Georges St. Pierre, has ruled the 170-pound roost for the past six years.

"The Great," who company president Dana White essentially ruled a "choker" in big fights, has been maddeningly inconsistent at middleweight since a first round loss to division champion Anderson Silva in 2007.

He racked up an impressive record (6-3) since that time, but has struggled against the top tier of the division, losing to Thales Leites, Chael Sonnen and Yushin Okami.

Perhaps he feels that shedding a few pounds will get him over the hump.

But will it? And is Rick Story a better match-up than Anthony Johnson would have been?

UFC on Versus 4, which goes down June 26 at the Consol Energy Center in Pittsburgh, Pennsylvania, will now feature a main event of Nate Marquardt vs. Rick Story.

In addition, heavy-hitting heavyweights Pat Barry and Cheick Kongo will sling leather in the co-main event of the evening.

Also on the card, Joe Stevenson will make his featherweight debut against Javier Vazquez, while Manny Gamburyan welcomes Tyson Griffin to the 145-pound division.

Stay tuned to MMAmania.com for future updates to this still-developing fight card.