In a column for Sky Sport, Matthaus wrote: "After the departures of [Thomas] Muller and [Leroy] Sane and the long injury break for [Jamal] Musiala, Bayern Munich had to respond with quality. Luis Diaz has proven his quality in the Premier League. He's fast and strong in tackles. With him, Bayern have more options up front. He played as a left winger, a central midfielder, and a second striker at Liverpool. He could play behind Kane at Bayern, just like [Serge] Gnabry or [Michael] Olise. But if Diaz costs €75 million, he should be a permanent fixture in one position."
He added: "However, Diaz is already 28 years old, while Nick Woltemade is only 23. If they pay €75 million for a player five years older, they must have great confidence in Diaz. If one were mean, one could ask: Why doesn't Bayern have this trust in Woltemade, who has already committed to FCB? VfB Stuttgart would probably have been satisfied with the amount Diaz costs."
Reflecting on Bayern's search for a winger and their desperation to find one this summer, the ex-Bayern midfielder said: "Bayern's search for a left winger was similar to the search for a coach a year ago. If they end up as lucky with Diaz as they were with Vincent Kompany, they can be glad that the names previously contacted by the club didn't opt for a move to Munich. You don't always get everything you want; that's the way business works. It's not like it used to be, when you could literally walk to Real Madrid and Bayern Munich."