Newcastle United have a problem this summer, and it will not be easy to solve. The Magpies might be in the market for a striker, and they definitely will be if Callum Wilson leaves the club. The 32-year-old’s future is currently up in the air, with his Toon contract due to expire next summer. It has been reported that members of the Newcastle hierarchy would like to sell Wilson, while it has been suggested that the Newcastle number nine is up for a new challenge. Alexander Isak needs supportIf Wilson does leave St James’ Park, Newcastle absolutely must sign a striker. Eddie Howe will need some…