Union Berlin started pre-season training on Wednesday but their top striker Taiwo Awoniyi only made a brief appearance to bid farewell to the other players and staff. Awoniyi, 24, who has scored 15 Bundesliga goals for Union last season, is linked with a move to promoted English Premier League club Nottingham Forest. He reportedly has a €20 million ($21.1 million) release clause in his Union contract. Coach Urs Fischer did not have a full squad available Wednesday, after performance tests the previous two days, as several national team players are still on holiday. Newly signed Danilho Doekhi …