The Turkish club attempted to recruit the 27-year-old during the summer transfer window, but Newcastle rejected an offer reportedly worth £17 million after their new head coach identified Willock as an important part of his plans.
Willock's future had appeared uncertain after a limited role under Eddie Howe last season and with his contract entering its final year. Besiktas made him a leading target, with Adali claiming that the club had gone as far as bringing the midfielder's family to Istanbul and selecting a house in anticipation of a move.
However, the arrival of Jaissle has changed the situation. The Newcastle manager has given Willock a more prominent role, and the midfielder has responded with strong performances and three goals this season.
Adali has continued to express an interest in bringing him to Turkey, but Jaissle was dismissive when asked about the latest comments.
“Yeah, I hear that every day. I think he's talking about it also every day!” the Newcastle boss said.
The German then made clear that the midfielder remains firmly in his plans at St James' Park.
“It's our player. We're really happy with him, and I think you see that also on the pitch. He's a top, top player; he can deliver unbelievable performances, and I see even more potential with him, so we are happy that he's here.”
Willock's revival represents a significant change from the uncertainty surrounding his position earlier in the year. Having struggled for regular opportunities last season, he has benefited from the confidence shown by Jaissle and is now contributing more consistently to Newcastle's attack.
His goalscoring form has strengthened the manager's argument for retaining him, particularly as Newcastle seek to maintain their progress in the Premier League. Willock's ability to carry the ball forward and arrive in dangerous positions offers an additional attacking threat from midfield.
Besiktas, meanwhile, must consider whether another approach would be worthwhile after Newcastle rejected their previous offer. The Turkish side's interest is clear, but Jaissle's public backing suggests the English club have little appetite for negotiating a January departure.
Newcastle's position is also reinforced by Willock's importance to the current squad. The manager has indicated that he believes the midfielder can improve further, leaving the club with a strong sporting reason to resist another bid.
For Willock, the immediate priority is to maintain his performances and help Newcastle achieve their ambitions. His improved form has put him in a stronger position than he occupied at the end of last season, and Jaissle's comments leave little doubt that the club want him to remain.
Unless Newcastle United's stance changes substantially, Besiktas appear unlikely to find an easy route to securing the midfielder when the January transfer window opens.