VfB Stuttgart have triggered the purchase option for Germany striker Deniz Undav but it remains unclear whether he will be staying at the Bundesliga runners-up, Sky TV reported on Saturday. Undav played on loan at Stuttgart last term from Premier League side Brighton & Hove Albion who for their part have an option to buy him back – which would lead to new talks. The purchase option is for around €20 million ($21.4 million). Undav, 27, has said he wants to stay in Stuttgart and is said to have agreed personal terms on a contract over three or four years. He scored 19 goals in all competitions f…