The Lions completed the signing of the Belgium intentional today on a three-year deal.
A source close to the club told Turkish-football.com that they opted for Cavanda as he was available at a cheaper price and knows the Super Lig in addition to already being match fit.
Debuchy has struggled with injuries over the past season and was loaned out to Ligue 1 outfit Bordeaux over the second half of last season.
Galatasaray sporting director Levent Nazifoglu confirmed that Debuchy was offered by his agent to the Istanbul giants just last week.
“Mathieu Debuchy was offered to Galatasaray through his agent on a loan deal,” Nazifoglu was quoted as saying by Turkish-football.com.
West Ham are also in the race to sign Debuchy according to Turkish sports newspaper Fanatik.
The sports paper has close ties to Hammers boss Slaven Bilic from his time coaching Besiktas. Per the source, the Hammers have been keen on bringing in the experienced full-back to add depth next season.