By Dan Marsh Erik ten Hag has told Marcus Rashford that he can be “unstoppable” with the right attitude ahead of Sunday’s highly anticipated Manchester derby. Ten Hag takes his Manchester United team to the Etihad in need of a result after overseeing the club’s worst start to a season in decades. That has led to scrutiny over his long-term future with Sir Jim Ratcliffe, the club’s new part-owner, set to assess every aspect of the club’s operations between now and the end of the season. The former Ajax chief enjoyed a fine maiden year at the helm and Rashford’s form played a significant part in…