The 31-year-old was left without a fresh destination once the transfer window closed without any club submitting an offer, forcing Rayo to include him among their registered players regardless of Beñat San José's plans for him.
It marks an unexpected turn for a striker who had spent much of pre-season training apart from the rest of the squad while the club searched for a way to move him on.
Asked directly about the forward's situation, San José was candid about the uncertainty surrounding his role.
"It's a complicated situation. When I arrived, I was told they were in talks with Raúl to reach a solution, but I think the situation is going to change now, so I'm waiting for the club to tell me what the final situation with the player will be," the Rayo head coach said.
"I respect him a lot, but obviously I go by what the club tells me, because it's a decision that had been under discussion even before I arrived."
De Tomás returns to the fold following an unsuccessful loan spell in Qatar with Al Wakrah, where he managed just a handful of appearances before an injury in early 2026 led to the early termination of the deal.
He remains under contract at Rayo until June 2027, though the club had been actively looking to offload him at the start of the season, keeping him separated from his teammates during training.
His path back into first-team contention now depends on developments the club has yet to make public, with San José stopping short of confirming whether the forward would be reintegrated into full training or remain on the periphery of the squad.
The situation echoes a turbulent recent period for De Tomás, whose previous exit attempt last year included a training-ground bust-up before he eventually left for Qatar in search of regular football.
For Rayo, registering a player they had been trying to offload represents an unusual outcome to the transfer window, and the uncertainty over his future looks set to continue for now, with the final word resting on communication that has yet to arrive from the club's hierarchy.