The Leverkusen captain is quoted by German website Spox expressing that he feels the deal has a finality about it, and Son is moving on.
He also communicated his amazement at the suddenness of the deal, which came as Leverkusen were preparing for a crucial Champions League qualifier.
He said: "(It is) astonishing that he was no longer there at once.
"Players change clubs, if he has (decided to), then he is not a part of this team more."
Son was well liked by the Leverkusen staff and players, having spent two seasons with the German side after signing from Hamburg in 2013. It says a lot about his popularity, impact, and respect that his loss is being so keenly felt by his soon-to-be ex-teammates.
German outlet Sport1 has reported that Heung-Min Son passed his medical at Tottenham Hotspur, and has a four-year deal on the table from the club.
Added to Bender's shock, Son's departure less than 24 hours before a crucial game upset his manager Roger Schmidt, and teammate Hakan Calhanoglu, who told Sport1: "I think it's just a pity that he is ill advised by his dad or agent, just before so a game like against Lazio this did not have to be.
Bender was last week reported to be a target for Arsenal by Italian website Tuttomercatoweb. His own oublicly expressed shock at a sudden pre-deadline day deal for his teammate suggests he has no plans of being tempted away in similar circumstances, especially now they have qualified for the Champions League.