Ridvan Yilmaz is close to signing a five year deal with Rangers.
A fee of around $5 million has been agreed for the Turkish player, who is currently playing for Rangers.
The player made it clear to several clubs that he wanted to join Giovanni van Bronckhorst's side.
Rangers' sporting director Ross Wilson had been working on replacements for Calvin Bassey, the club's all-time leading scorer.
Rangers are working on further deals during the current transfer window, after Ben Davies joined fromLiverpool.
Rangers' current left-back Borna Barisic has been the subject of interest from several clubs, but no offers have been made that match the club's valuation.
Yilmaz has six international caps and has made 62 appearances in all competition for Besiktas.
He will be Van Bronckhorst's seventh signing of the summer.
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It will be hard for a player to replace Calvin Bassey.
Bassey was incredible towards the end of the season and the run that Rangers had. I think that he's attracting clubs because he's versatile, he can play left-back, left of a three, and the center of three. Bassey is a player that teams look at to cover a lot of positions and he is in that category.
The performances towards the end of the season for Rangers were outstanding and you felt as if the team got a lot of belief from that. They didn't have to protect the back line as much because of his pace. He will be missed by Rangers if he has to leave.
"Players have left in the past and then replaced, but I think this one could be a bit difficult because of thatVersatility." Rangers will need some kind of protection. Borna Barisic has been linked with moving away. They need someone to come in at left-back, and someone that can play on the left side of a two or a three, as well as off the back of Bassey's departure.
I think it's time to label the young boy because he is very harsh on such a young boy. He can defend one-on-ones, he's good with the ball, he's fast, and he will be an attractive signing for someone.
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Giovanni van Bronckhorst said he expects Antonio Colak to do well.
He can score goals, and he's a very good forward. He did a lot of damage at the start of last season.
It is a new season and we want to be successful in all the competition we play so we need the squad to be able to do that."
We are happy that he will be joining us.
The transfer window will close at 11pm on September 1st.
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