The 25-year old Serbian attacking midfielder joined the Saints from Dutch club FC Twente on Tuesday and the St Mary's boss feels he will be the right man to step into the hole left by Adam Lallana who has departed for Liverpool.
"We're very happy that Tadic is coming in. He's a great player," Koeman told Southampton's YouTube channel.
"He's 25 and he has a great future, and I think he can now reach the level that we need and a player needs to be at in the Premier League.
"When we lost a great player in Lallana, we were looking for a similar player in that position, and we've found it."
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