Stuttgart head coach Sebastian Hoeness has been impressed by the way Martin O'Neill has transformed a "turbulent" season at Celtic as the teams prepare to meet in the first leg of their Europa League play-off.
O'Neill, 73, is in his second spell as interim boss, stepping in after the departures of Brendan Rodgers and Wilfried Nancy.
The Scottish champions have gone 10 games unbeaten since O'Neill returned in January and now lie three points behind Premiership leaders Hearts with a game in hand.
Former Aston Villa, Sunderland and Republic of Ireland boss O'Neill, who was at Celtic between 2000 and 2005, will take charge of his 1000th game as a manager against the team that sits fourth in the Bundesliga.
Hoeness said: "The highest respect for his career. It's a life achievement, over 1000 games is unbelievable.
"I expect a lot. They are a team who have had a very turbulent season with lots of changes of coach.
"The current coach has a special history here and he is a very experienced coach. It's a team who have really found form recently after they had ups and downs.
"It's one of the toughest draws we could have got but one of the most exciting, given we have the chance to play in this historic stadium.
"I think that gives the team power and energy and we'll have to be able to counter that but we're prepared for the task ahead.
"It'll be very challenging but these are the games you want to play when you're in Europe so we're going to try and create a good position for ourselves going into the second game."