Sky Bet have suspended betting on Alvaro Negredo's next club after the Sevilla striker was backed at as short as 1/12 to join Manchester City.
The online bookmaker have reported the run of bets amid Spanish media reports that City have launched a bid, thought to be in the region of £24m.
The Premier League runners-up have been odds-on to secure the Spain international's services for over a fortnight but betting was eventually suspended on Wednesday afternoon as interest heightened.
Negredo, 27, scored 25 goals for the Andalucian outfit as they endured a disappointing campaign, finishing ninth in La Liga.
Former team-mate Jesus Navas has already swapped the Ramon Sanchez Pizjuan for the Etihad Stadium, joining fellow midfielder Fernandinho in signing for City this summer, while striker Carlos Tevez has left for Juventus.
Sky Bet Football Trader Chris Spicer said: "Atletico Madrid had been backed to land Negredo following Falcao's departure but were overtaken by City in the betting.
"Additional firepower looks essential given their troubles in front of goal last season and they have previously been backed to bring in Isco and Edinson Cavani, but Negredo now looks to be their man."