Southampton have told Napoli that if they are not prepared to accept the offer on the table for striker Manolo Gabbiadini then they will walk away.
The Saints are one of a host of Premier League clubs interested in the Italian hitman, though they have gone a step further than most by making an official bid.
The offer stands at €16m plus a further €2m to €3m in bonus payments; Napoli have been claimed to be looking for a minimum of €20m.
According to Italian radio station Radio Crc, the Premier League side have now made clear to Napoli that if they are not willing to accept the offer a new one will not be forthcoming.
Indeed, Southampton would quickly switch their attention to Real Madrid youngster Mariano.
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The 23-year-old is viewed as an alternative to Gabbiadini by the Saints, who will move on to trying to land him if no deal can be done for the Napoli man.
Mariano has made three appearances in La Liga for Real Madrid so far this season, scoring once.
The 23-year-old has risen through the youth ranks at the Bernabeu, turning out for Real Madrid's C and Castilla teams.
