Losing to AEK Athens is a major financial blow for Celtic, as they failed to qualify for the Champions League.
The Celtic Park outfit crashed out of the Champions League after a 3-2 aggregate defeat against the Greek side. Whilst it is certainly a financial hit for the club, Brendan Rodgers will need to lift the spirits of his players and get them firing domestically. Celtic have long struggled in Europe, but on Scottish turf, the Hoops look unstoppable.
After winning successive trebles, Brendan Rodgers can not afford to rest on his laurels. Celtic must keep improving if they are to remain the dominant force in Scotland. With cross-city rivals Rangers showing some real intent and ambition by employing Liverpool legend Steven Gerrard, it is vital Rodgers keeps Celtic moving forward.
With that in mind, these two players will need to be at the top of their games if Celtic are to make it three trebles in a row.
The 33-year-old captain will need to show he is still at the top of the game if he is to drive Celtic to a third successive treble winning season.
Scott Brown has the ability to dominate the middle of the field for Celtic, however, whether he can keep his high energy game up as he enters the latter stages of his career is unknown.
A crucial player for Celtic, Brendan Rodgers will need his captain in form over a gruelling season, if they are to win all three domestic competitions again.
The Northern Irish manager will know how important the creative talents of Scott Sinclair are to the side. He has the sheer quality and talent to chance a game, and put an opposition defence to the sword.
He slightly dropped off last season, after an excellent first season in Glasgow after arriving from Aston Villa. The 29-year-old experienced winger will be relied on heavily if Celtic are to complete another treble.