Question: When was the undefeated Russian mixed martial artist of Avar heritage born who was a MMA star and trains with Magomedrasul Mukhtarovich Gazimagomedov?

Context paragraphs:
Khabib Nurmagomedov: Khabib Abdulmanapovich Nurmagomedov (Russian: Хабиб Абдулманапович Нурмагомедов ; Avar: ХIабиб ГӀабдулманапил НурмухӀамадов ; born September 20, 1988) is an undefeated Russian mixed martial artist of Avar heritage.  He is a two time Combat Sambo World Champion, a wrestler and a judo black belt who currently fights in the Lightweight division of the Ultimate Fighting Championship.  He currently holds one of the longest undefeated streaks in MMA with 24 wins.  As of 17 November 2016, he is ranked the #1 contender in the UFC Lightweight division and #12 in official UFC pound-for-pound rankings and numerous other publications.

Gadzhimurad Antigulov: Gadzhimurad Antigualov (Russian: Гаджимурад Антигулов ; born January 1, 1989) is a Russian mixed martial artist of Avar heritage who currently fights in Light Heavyweight division in the Ultimate Fighting Championship (UFC).  He was the two times Light Heavyweight champion for Absolute Championship Berkut.  He is currently the #15 ranked light heavyweight in UFC rankings as of 2 July 2017.

Magomedrasul Khasbulaev: Magomedrasul Magomedalievich Khasbulaev (Russian: Магомедрасул Магомедалиевич Хасбулаев ; born October 23, 1986) is a Russian mixed martial artist of Avar heritage at one time fought in the Featherweight division for the Bellator Fighting Championships.  Khasbulaev is a Combat Sambo Russia National Champion.  He currently competes in World Fighting Championship Akhmat and Absolute Championship Berkut (ACB).

Shamil Abdurakhimov: Shamil Gentovich Abdurakhimov (Russian: Шамиль Гентович Абдурахимов ; born September 2, 1981 in Dagestan) is a Russian of Avar heritage mixed martial artist, who is currently fighting in the heavyweight division for the Ultimate Fighting Championship.  He is currently the #15 ranked heavyweight in UFC rankings as of 21 November, 2016.

Murad Machaev: Murad Magomedkhanovich Machaev (Russian: Мурад Магомедханович Мачаев ; born December 3, 1986 in Dagestan) is a Russian mixed martial artist of Avar heritage who currently fighting in the lightweight division for the Eurasia Fight Nights Global (EFN), Bellator MMA veteran, he is the winner of the 2011 Fedor Emelianenko Cup.

Sultan Aliev: Sultan Magomedbegovich Aliev (Russian: Султан Магомедбегович Алиев ; Avar: Султан Гӏалиев ; born September 17, 1984, Dagestan) is an Avar heritage born in Russia mixed martial artist and sambist, who competes in the Welterweight division for the Ultimate Fighting Championship.  He is also a veteran of the ProFC organization and Bellator MMA.

Abubakar Nurmagomedov: Abubakar Magomedovich Nurmagomedov (Russian: Абубакар Магомедович Нурмагомедов ; Avar: АбубакIар МухӀамадович НурмухӀамадов ; born November 13, 1989) is a Russian mixed martial artist of Avar heritage, who currently fights in the Welterweight division of the World Series of Fighting.  He is a Combat Sambo World Championships bronze medalist and Russian national combat sambo champion.

Ramazan Emeev: Ramazan Dadaevich Emeev (Russian: Рамазан Дадаевич Эмеев ; born May 20, 1987) is a Russian mixed martial artist of Avar heritage.  He is Combat Sambo World Champion who currently fights in the Middleweight division of the Ultimate Fighting Championship.  Former M-1 Global middleweight champion.

Magomedrasul Gazimagomedov: Magomedrasul Mukhtarovich Gazimagomedov (Russian: Магомедрасул Мухтарович Газимагомедов ; born April 8, 1991 in Dagestan) is a Russian of Tindian heritage freestyle wrestler.  Grand Master of Sports in Freestyle Wrestling.  He is winner Russian National Freestyle Wrestling Championships 2015.  In the quarterfinals match he beat to World Champion Khetag Tsabolov of North Ossetia–Alania.  European Games champion, who competed in the men's freestyle 70 kg category at the 2015 European Games and won the gold medal.  In preseason he trains with MMA stars Rustam Khabilov and Khabib Nurmagomedov.  He won gold medal at the 2015 World Wrestling Championships at Men's freestyle 70 kg.

Zabit Magomedsharipov: Zabit Magomedsharipov (born 1 March 1991 in Dagestan) is a Russian mixed martial artist of Avar heritage.  He currently fights in the Featherweight division of the Ultimate Fighting Championship.  He is former ACB Featherweight champion.

Supporting paragraphs: Magomedrasul Gazimagomedov Khabib Nurmagomedov
Answer: September 20, 1988