Alexander Isak has been challenged to become the best striker in the world by Newcastle boss Eddie Howe. A month ago Howe threw down the gauntlet to his star Swedish goalscorer and demanded he play at the top of his game before thinking of a new contract. That triggered Isak into action and he has scored in his last four Newcastle games, including a three game winning streak. The 25 year-old is one of the most complete strikers after recovering his full fitness after injury. He has been linked