The Las Vegas native, who turns 25 next month, fought with heart throughout the contest to see out a bruising encounter on the scorecards.
Allakhverdiev suffered a bad cut in the eighth round, which only served to spur him on, although Vargas did enought to take the fight 117-111, 115-113 (twice) to remain undefeated.
There was also a victory for lightweight contender Ray Beltran on the MGM Grand bill as the tough puncher came through late replacemenrt Arash Usmanee.
Beltran took a couple of rounds to work out Usmanee’s style, but in the end scored a decisive 118-110, 117-111 (twice) triumph on the scoresheets.
Earlier, Bryan Vasquez retained his interim WBA super-featherweight title after the Costa Rican ended the unbeaten streak of Jose Felix Jr. following a hard-fought and sometimes dirty twelve rounds.
The 26 year-old did just enought to edge the closer rounds to see out a 117-110, 114-113 (twice) win on the three ringside judges scorecards to improve his record to 33-1.
Light-heavyweight contender Seanie Monaghan inproved to 21-0 with a fifth round stoppage win over Joe McCreedy, whilst Oscar Valdez pushed his career victories to double figures, without loss by halting Adrian Perez in the fourth.
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