Ayala, 25, was a contender for Boro's Player of the Season award last term as they were promoted to the Premier League, but with only a year left on his contract, has been a source of worry for some fans.
This concern was amplified by manager Aitor Karanka's transfer activity in the defensive department, and the fact that the former Liverpool and Norwich City man did not feature in the first game of Middlesbrough's pre-season campaign, a 6-0 victory over York City.
Gibson and Ayala miss York friendly through injury
Ayala's usual defensive partner Ben Gibson was also missing from that game, but Karanka confirmed that both players had been missing through injury.
“Both of them are injured, Ben and Dani are injured,” he said. “Both of them were (injured) the same day after a training session, he (Dani) felt his ankle again.”
The Spaniard missed a significant part of the season last year with a troublesome and mysterious ankle injury, and Boro's form suffered dramatically in his absence.
Transfer quartet could be Boro-bound this week
And the Gazette claim that the club are hopeful of bringing the experienced Serbian in later this week, though the Teessiders face stiff competition from Arsenal and Liverpool for his signature.
The club are also looking to tie up deals for Valencia pair Álvaro Negredo and Antonio Barragán, as well as former loan star Gastón Ramírez.
Ramírez has agreed terms on his return to Middlesbrough, but the club are still waiting to hear the result of his work permit application.