The former Spain international has long been linked with Liverpool, but with the Reds’ interest rumoured to have cooled the North East duo now lead the race for his signature from an English perspective.
Capel has endured a mixed spell in Portugal, and having only managed one goal in 23 appearances this term the Lisbon side are thought to be ready to sell.
Both Newcastle and Sunderland are believed to be willing to match his £4m valuation, which could set up a transfer tug-of-war in a few months’ time.
The former appear the more likely side to get the 26-year-old, with the Magpies guaranteed to be in the top tier next season.
Sunderland on the other hand are embroiled in a relegation scrap, but could look to make a serious move for Capel if they maintain their Premier League status.
The pacey wide-man was once hailed as one of Spain’s top talents, but since leaving Sevilla his form has dipped on the back of a number of injury problems.