The Manchester City midfielder spent four key years playing under Klopp when he was in charge of Bundesliga side Borussia Dortmund between 2011 and 2015.
It was a hugely successful period with Dortmund winning the Bundesliga title, German Cup, German Super Cup as well as reaching the 2013 Champions League final.
Gundogan also made his breakthrough into the German national team in that period, forging a reputation as one of Europe's most impressive midfield talents.
And Ilkay says was Klopp was instrumental in shaping his professional development both through the good times and the bad.
“I had four fantastic years with Jürgen. We won a lot of things together, we lived through many different experiences together, we had our lows, too.
"I came to Dortmund from a relatively small team (Nuremburg) and I struggled during my first six months to find my place there. I was a bit shy and, to be honest, I wasn’t brave enough do certain things.
"But thanks to the help of my team-mates, and with the help of Jürgen and his staff, too, I managed to improve.
I was finally able to find my way and my place. It was hard, but I learned a lot and I tried to assimilate everything at that point.
"Jürgen played a very important role in all that and I’m very grateful to have played in that team at such a high level for so many years. I learned a lot and I managed to improve my game a lot, too.
"Those days left a mark on my career. Those were my first steps in European football, too, because it was an opportunity that I hadn’t had before. So that’s another thing I have to thank him for."
Klopp has helped Liverpool rediscover their attacking edge with feared trio of Mohamed Salah, Sadio Mane and Roberto Firmino forming a potent front trio.
And Gundogan knows how Klopp will seek to cover every base as he prepares his team for a two-legged tie that has caught Europe's imagination.
"Jürgen is a terrific coach and he’s capable of motivating his team ahead of every game. He doesn’t mind if it’s a friendly between amateur teams or a Champions League final, for example.
"He’s a top guy who knows how to deal with his players, how to treat them and how to motivate them. And he’s proving all that again with Liverpool - their attack is incredibly strong.
"So they aren't an easy team to beat but we need to do so."
If the German international and his team-mates needed any extra motivation ahead of the tie, it lies in the fact that City's sole defeat in the Premier League this season came at the hands of the Merseysiders with Liverpool edging a seven-goal Anfield thriller in January.
So the 27-year-old says City are anxious to put the record straight on their return to Merseyside this week.
"But we’re aware why this happened, although we performed pretty well that day," Ilkay reflected.
"Obviously, going back to Anfield for the first-leg game is a great motivation for us. We’ll try to play well and get a good result for the second leg. I think we’re aware of our strengths and we know what we’re capable of. We want to prove that in both games."