Porto have signed Watford defender Miguel Layun on a one-year loan with the option of a permanent contract in a deal thought to be worth around £4.4m.
The Mexican joins fellow countryman Jesus Corona, who has just joined Porto on a five-year-deal.
Layun, who can play on the left of the defence or midfield, joined Watford from Granada in January and helped them win promotion to the Premier League.
He scored their opening goal on the first day of the season in a 2-2 draw with Everton.