Jake Shields won a battle of world-ranked fighters when he forced Robbie Lawler to tap out from a guillotine choke at 2:02 of the first round in the main event from the Scottrade Center in St. Louis, Mo. It was Shields' 12th victory in a row.

In a startling display of explosiveness, unbeaten, hard-hitting heavyweight Brett Rogers overwhelmed former UFC heavyweight champion Andrei Arlovski, finishing him off after just 22 seconds had elapsed in the first round.

Talented, world-class Cesar Gracie Jiu-Jitsu black belt Nick Diaz continued to triumph impressively, stopping game but outgunned Scott Smith in the third round.

After two competitive rounds, southpaw Joe “The Diesel” Riggs came on strongly to dominate the third en route to registering a unanimous decision over Phil Baroni in a welterweight fight

“Iron’’ Mike Whitehead scored the biggest victory of his career with a close, unanimous decision over two-time NCAA Division I national wrestling champion Kevin Randleman in a light heavyweight bout.

Jake Shields, a world-ranked welterweight, submitted (guillotine choke) world-rated middleweight, “Ruthless’’ Robbie Lawler, in the STRIKEFORCE main event before 8,867 who turned out at the Scottrade Center for the most significant mixed martial arts event in the history of the Gateway City.

Shields’ 12th consecutive victory in a match fought at a catch weight of 182 pounds capped a wild and entertaining evening of MMA highlighted by undefeated Brett “The Grim’’ Rogers’ shocking 22-second knockout over former UFC heavyweight champion Andrei “Pitbull’’ Arlovski and another impressive performance by talented, world-class Nick Diaz, who submitted (rear naked choke) hard-trying Scott “Hands Of Steel’’ Smith at 1:41 of the of the third round.

In other results, southpaw Joe “The Diesel” Riggs registered a unanimous decision over Phil Baroni in a welterweight scrap and “Iron’’ Mike Whitehead scored the biggest victory of his career with a unanimous decision over two-time NCAA Division I national wrestling champion Kevin Randleman in a light heavyweight bout.

San Francisco’s Shields (23-4-1), the grappler moving up in weight, forced the slugger, Lawler (16-5, 1 NC), of nearby Granite City, Ill., to tap out at 2:02 of the opening round from a guillotine choke. The defeat ended a six-fight unbeaten streak (5-0, 1 NC) for Lawler.

“This was a great fight and I thank Robbie for the opportunity,’’ said Shields, who, along with Diaz, is a Cesar Gracie Brazilian Jiu-Jitsu black belt. “He is a great fighter but this was just my night.’’

Rogers’ victory, while perhaps not totally unexpected, figures to have the fans talking for a long time. After missing with his first punch, a right hook, Rogers (10-0), of St. Paul, Minn., landed a flush left hook, a right and another left hook that sent Arlovski (15-7), of Chicago, crumbling to the canvas. The referee stepped in and halted the proceedings immediately.

“I’ve always said that I can hurt people with my power and I proved it again tonight,’’ Rogers said. “Hopefully, this fight will get me into the top 10. Once, I touch you it is over. I will fight anybody.’’

Diaz (20-7), of Stockton, Calif., mostly dominated Smith (17-6, 1 NC) of Elk Grove, Calif. Diaz, who was coming off an easy victory over Frank Shamrock in April, seemed to do as he pleased for the most part. He out-punched the puncher, hurting Smith on numerous occasions. Known for miraculous comebacks, Smith had no answer on this night, going down twice, the last time from body shots.

“I’m not sure who I’ll fight next or if it is at 160, 170 or 180,’’ said Diaz after the fight was stopped at 3:38 of the third. “But I am happy with this fight.’’

Riggs (30-10), of Phoenix, Ariz., won by the scores of 30-27 on the three judges’ scorecards. After managing to bottle up Baroni and take the first two rounds, Riggs, despite two broken hands, dominated the third. “I want to fight Jake Shields,’’ Riggs said afterward.

Baroni (13-11) of Las Vegas by way of Long Island, NY, had a three fight winning streak end.

In the telecast’s opening bout, Whitehead (24-7), of Las Vegas, outpointed Randleman (17-13) of Las Vegas by the scores of 29-28 three times. It was the second straight victory for Whitehead, who is 15-1 in his last 16 fights. Randleman was fighting for first time since May 2008 and only the second time since October 2006.

Saturday’s non-televised results: Pat Benson, St. Louis, submitted (triangle choke) Dave Cochran, St. Louis, at 2:18 of the first round (155 pounds); Lucas Lopes, Columbia, Mo., won by disqualification (illegal knee strike) over Scott Ventimiglia, Wood River, Ill., at 3:26 of the first round (185 pounds); Tyron Woodley, St. Louis, submitted (choke) Salvador Woods, Granite City, Ill., at 4:20 of the first round (170 pounds); Booker DeRousse, St. Genevieve, Mo., TKO 1 (strikes, 4:20) over James Woods, St. Peters, Mo. (205 pounds); Mike Kyle, San Jose, Calif., TKO 2 (strikes, 4:05) over Rafael “Feijao” Cavalcante, Brazil (205 pounds); and Jesse Finney, St. Louis, submitted (keylock) Josh Bumgarner, Waterloo, Iowa, at 1:55 of the first round (175 pounds).