Germany put on a show in their opener as they delivered a thrashing of Curacao for the biggest win of the opening round.
But an exciting Ivory Coast side, brimming with the confidence from a late victory against Ecuador in their opener, posed an altogether different challenge.
Diomande, linked with a move to Liverpool, showcased his pace and raw ability on the left flank for the Ivorians, while Manchester United winger Amad, Kessie and 20-year-old Oulai all caused problems for the German defence that has now kept just one clean sheet in its past six matches.
Ultimately though, Germany were rescued by the quality of their substitutes.
With his side trailing 1-0, Nagelsmann made a triple change in the 60th minute, bringing on Jamie Leweling, Amiri and Undav – with the latter duo combining for the equaliser only eight minutes later.
Undav then struck a second to take his tally to nine goals in just 11 appearances for Germany and make his case for a starting spot again, helping his side put embarrassing group-stage exits in 2018 and 2022 behind them.
Ivory Coast, meanwhile, can take a lot of heart from their performance despite the last-gasp defeat.
This group of players remain well-placed to achieve a feat that eluded the likes of Didier Drogba, Yaya Toure, Kolo Toure and Salomon Kalou before them – taking their country to the knockout stages of a World Cup.