PSV returned to winning ways with a 2-1 victory over Excelsior on Saturday, a result that gained further importance after both Ajax and Feyenoord dropped points.

The Eindhoven club also reverted to a more familiar system, while Joey Veerman made what is expected to be his final appearance before completing his move to Borussia Dortmund, subject to his medical examination.

For former PSV and Ajax coach Aad de Mos, the result offered encouragement, but he believes there remains work to do at the back.

Speaking to PSV watcher Rik Elfrink of Eindhovens Dagblad, De Mos questioned whether Ryan Flamingo is reliable enough to occupy a regular defensive role for the reigning champions.

Flamingo was involved in the build-up to Excelsior's equaliser, and De Mos believes the moment highlighted concerns that have persisted around the defender.

“Flamingo isn’t stable enough. You can’t have that in this period. In terms of building up, he isn’t great either. Then it needs to be defensively top-class if you’re going to be able to hold your own, but that’s also not the case. Maybe for him it’s better to make a transfer,” De Mos said.

The former coach did, however, suggest that Flamingo could still be part of Bosz's squad in a different role.

“Or. PSV must keep him for emergencies. He can of course also work as a number 6.”

That versatility could still make Flamingo useful to Bosz, but De Mos believes PSV need a more established option to strengthen the heart of their defence.

Lutsharel Geertruida has been PSV's primary defensive target for much of the summer, with the club continuing to pursue a deal with RB Leipzig.

The former Feyenoord defender is regarded as a player with greater experience and international pedigree, and De Mos believes those qualities should make him the preferred option.

“Then it is important to sign a good player. One who is further than Flamingo, is also an international. Let’s wait and see whether it will be a purchase or a loan,” De Mos said.

For PSV, the structure of the proposed deal remains crucial. A permanent transfer would represent a substantial financial commitment, while a loan has been considered a more realistic route.

The Eindhoven side have continued to hold talks over Geertruida, who is also understood to favour a move to PSV.

With the transfer window approaching its conclusion, De Mos' assessment adds further weight to the argument that defensive reinforcement remains one of Bosz's key priorities.

PSV's next challenge comes against FC Groningen on Sunday afternoon, with the club looking to build on the momentum gained at Excelsior while the transfer window enters its decisive phase.