Up until last month, Yuriy Vernydub had never stepped onto the biggest stage of European football, let alone succeeded on it.

That all changed when his Sheriff Tiraspol side shocked the world in his and the Moldovan club's first appearance in the Champions League group stage.

First, the club based in the tiny breakaway state of Transnistria downed regular Champions League knockout stage participants Shakhtar Donetsk.

Then, against all odds, the minnows defeated 13-time European champions Real Madrid at the Santiago Bernabeu.

But the 55-year-old Ukrainian coach, who has spent most of his career in the post-Soviet space, remains humble.

"I'm grateful to my guys for what they did," Sheriff's head coach said after leaving Madrid with three points.

People close to Vernydub describe him as persistent and a hardliner who never backs down from getting his way.

"You cannot argue with him," his son Vitaliy Vernydub, who is a professional footballer and played under his father for several years, said on Ukrainian television.

Born in the northwestern Ukrainian city of Zhytomyr, a transportation hub linking Kiev with Warsaw, Yuriy Vernydub started his professional career in his hometown as a player in 1983.

For years he bounced between low-profile clubs in Ukraine, far from the limelight of the top level of European football.

He finally got close in the twilight of his career, playing two matches with Zenit Saint Petersburg in the UEFA Cup.

But as both a player and then as a coach, Vernydub says he "dreamed" of participating in Europe's most prestigious competition, the Champions League.

In an interview with AFP, the Ukrainian shed light on his steadfast nature.

Accusing Moscow of supporting pro-Russian separatists in their fight against government forces in eastern Ukraine, he said he would now never accept an offer to work in Russia.

"That will probably remain true until the end of my life," Vernydub told AFP.

After his playing career ended in 2000 due to a knee injury, Vernydub launched his career as a coach, serving as an assistant with Metalurh Zaporizhzhia in the top flight of Ukrainian football.

His first head coaching role came in 2011 with Zorya Luhansk, a small-budget club which nonetheless challenged Ukrainian giants Shakhtar and Dynamo Kiev.

Against the odds, he led the club, who were forced to move stadiums after fighting erupted in eastern Ukraine in 2014, to the Europa League group stage in back-to-back seasons.

Footballers who have played for Vernydub say he helped them develop into better players.

One, 22-year-old goalkeeper Andriy Lunin, was purchased by Real Madrid in 2018 for a reported 8.5 million euros.

"He is a very good person and coach," Ukrainian international Oleksandr Karavayev, who played under Vernydub at Zorya, said on Instagram.

Karavayev, who now plays for Dynamo Kiev, pointed to Vernydub's "desire and trust" as helping him progress up the ladder of Ukrainian football and "get into the national team".

After a decade in various roles with Zorya, Vernydub eventually left in 2019 after reported disagreements over regular sales of the team's best players and new signings not agreed with the head coach.

"It is very difficult to start over every six months -- assembling a team, developing a style of play, fighting for results," Sergiy Rafailov, Zorya's former general director, said in a club statement after Vernydub's departure.

Vernydub then spent a season coaching in Belarus before moving to Transnistria's administrative hub Tiraspol over the winter.

"There was a chance to play in the Champions League," he explains.

Artyom Frankov, editor-in-chief of the Ukrainian Football Magazine, said the move was attractive to Vernydub because he was able to get more control over decisions.

"He himself can select the players he needs," Frankov told AFP.

On Tuesday, Sheriff travel to Italy to face former European champions Inter Milan.

"Clearly it will be very difficult," Vernydub says.

"But there is no need to be afraid. You need to go out and play."