He told the Evening Gazette: "The feeling here is that we want to make this a club on the up. We stabilised last season but we are looking to improve on what we achieved last season and we have set our sights on the top half of the table and beyond.
"The chairman spoke in the summer about recruitment and the need for change. We knew that we needed to be alert to the type of players becoming available that we are looking for, and we needed to be ready early in the summer.
"We watched Tuncay at the end of last season and we saw his qualities as a footballer. We moved as quickly as we could and it's fantastic that we've been able to bring a player of his calibre here.
"His pedigree with Fenerbahce and the Turkish national side is outstanding and he gives us a lot of options in terms of where he can play.
"He is hungry for the challenge to play in the Premier League."
Southgate knew that Boro had to move quickly to sign Tuncay and is delighted that the player fancies the challenge in England.
He said: "We were aware of the fact that other teams had been watching Tuncay but we were determined to make the approach.
"We know that he has played in the Champions League with Fenerbahce and has won the league title in his country but he wanted to test himself in the Premier League.
"At this stage of his career he wants to establish himself in another football environment and we are pleased to give him that opportunity.
"He's a proven player in Turkey and at international level and, while the Premiership will be all new to him, he is a quality player who hopefully will quickly adapt."
He added: "We have other targets in addition to those we have brought in and maybe we will have to give them time to settle in.
"There are obvious change of culture, particularly for a player like Tuncay.
"But we are confident that we can settle everyone in quickly and we are excited about the prospects ahead."