West Brom right-back Cristian Gamboa is having a medical at Celtic, sources tell Press Association Sport.
The 26-year-old Costa Rica international is in Glasgow with a view to signing for the Parkhead club.
Gamboa, who joined the Baggies in 2014 from Rosenborg, has won 47 caps for his country and played in the 2014 World Cup in Brazil.
He would offer competition to Mikael Lustig and Saidy Janko as Brendan Rodgers' side get set for their first Champions League campaign in three years.
The Hoops boss has already recruited Scott Sinclair, Moussa Dembele, Kolo Toure and Dorus de Vries to the Parkhead club this summer.
Speaking in Glasgow, Gamboa told Sky Sports: "I cannot say anything now, so we wait and see.
"I hope [by] the end of the day we have something.''
Asked how big an opportunity it could be for a player who has not played much for West Brom recently, he said: "It's big, it's really big'' before adding "we hope, we hope, we hope'' when asked if the deal was close to getting done.