By alley - Dec 16, 2016, 12:52 PM ET

F1: Red Bull won't part with Sainz - Horner

Amid wide-ranging speculation over a replacement for retired world champion Nico Rosberg, Red Bull Racing boss Christian Horner has dismissed the idea that one of his organization's top prospects – Toro Rosso racer Carlos Sainz Jr. – is on the list of candidates to join Lewis Hamilton on the Mercedes F1 team.

It has been suggested in European media that Sainz (pictured above), who has impressed with Red Bull's junior team, might be made available despite being contracted to Toro Rosso for 2017, since Red Bull Racing appears to be set for the forseeable future with Daniel Ricciardo and Max Verstappen. However, in an interview with BBC Radio 5 Live, Horner rejected the idea that this makes the Spaniard less valuable to Red Bull.

"Why would we do that? Carlos has done a great job. He is a Red Bull driver. We have invested in him to get him into F1 and they are all on long-term contracts," Horner said. "So it wouldn't make any sense to feed one of your main opponents with one of your assets."

Mercedes is believed to have settled on Willliams driver Valtteri Bottas as its preferred choice to replace Rosberg and

Williams has dropped hints it might be willing to make a deal to that effect

. Horner suggested that either the Finn or Mercedes junior Pascal Wehrlein – thought to be Mercedes' back-up choice if a deal cannot be concluded for Bottas – could emerge as stars if given the opportunity, noting that both Sebastian Vettel and Ricciardo (pictured, with Horner) became stars with Red Bull Racing only after being promoted from Toro Rosso.

"You give these guys a chance. Let's see what people can do in a front-running car," Horner said. "If they did take Wehrlein or Bottas, both are probably both capable of running right at the front.

"You just don't know until you give them the chance, which is what we did with Sebastian Vettel and Daniel Ricciardo."