Borussia Dortmund confirming Mats Hummels wants to join Bayern Munich is an example of the Bavarian giants' philosophy of weakening their Bundesliga rivals, says Olaf Thon.
After much speculation, Dortmund announced on Thrusday Hummels had informed the club he wished to make the switch to Bayern at the end of the season.
The centre-back came through the youth ranks at Bayern before making a permanent switch to Dortmund in 2009 having initially joined on loan a year beforehand.
Dortmund have already lost Robert Lewandowski and Mario Gotze to their title rivals in recent years, and Thon - a three-time Bundesliga winner with Bayern during a six-year spell at the club - believes the latest revelation shows the means by which the defending champions look to remain on top.
"Bayern weaken these opponents, like they did to Schalke with Manuel Neuer. That's their philosophy," he told Sport1.
"The fact they are doing it again now is linked to the many things that connect Hummels with Munich.
"If the captain does not leave a sinking ship, but a slick team, it is a shame. It's difficult to build a competition this way.
"In regards to competitiveness, Dortmund must not let him go. Hummels fits perfectly with [Jerome] Boateng because he is two footed and can play on the left side.
"With Manuel Neuer, the best goalkeeper in the world behind, they would strengthen the strongest contenders even further."
However, Thon believes it might be difficult for Bayern to stump up the cash to sign Hummels before his contract expires at the end of next season, adding: "I do not believe the sum would be high enough for Hummels to go there."