Fans leave the stands following last week's pre-season friendly between Celtic and Italian giants AC Milan at Parkhead. As they prepare for Monday night’s league opener against Dundee, the rumblings of discontent are not going away. Martin O'Neill welcomes AC Milan counterpart Ruben Amorim to Celtic Park for last week's pre-season friendly. PICTURE: PA (Andrew Milligan/PA)It was at the start of the 2003 season, indeed, when O’Neill first alluded to managing decline. Amid talk of losing Swedish star Larsson, and the smaller salaries available for any future replacements, O’Neill issued a warning.