Celtic return to Celtic Park on Sunday to face Hearts with Martin O'Neill under mounting scrutiny after a 4-1 Europa League defeat at Benfica in Lisbon.
The loss leaves Celtic without a point from two league-phase matches and extends their run to four defeats in their last five games across all competitions.
Hearts, last season's Scottish Premiership runners-up, now provide the next test as O'Neill tries to turn brief bright spells in Lisbon into a complete performance.
Another setback would add to questions about his position after an earlier spell of uncertainty over his future.
Slow start in Lisbon leaves Celtic chasing
Celtic fell behind early at Benfica and conceded three goals inside the opening 36 minutes.
They created chances after the break and hit the frame of the goal in both halves, but defensive lapses and poor finishing left them with a heavy loss.
O'Neill pointed to his players' second-half response and insisted Celtic can still reach the Europa League knockout stages.
He admitted the early concession hurt his side but highlighted the opportunities they carved out after halftime.
"The last thing you want to do is concede so early on," O'Neill told TNT Sports, adding that his team could have capitulated but produced what he called a terrific second-half display.
He said the performance gave him determination and repeated his belief that qualification remains possible over the six remaining games.
Supporters question first-half display
That optimism has not convinced everyone, with Tino Callaghan of the A Celtic Exchange Podcast telling Sky Sports News that fans still have reason to worry.
Callaghan said the manager was understandably stressing the positives but argued that the first half exposed deeper problems.
He said Celtic were "completely outstripped" at times and were not even competing during that period.
Callaghan linked the display to wider frustration among supporters that the club is no longer competing at Europe's top level.
He also recalled O'Neill's comments after the Rangers game, saying he thought there was a serious chance the manager would walk away before deciding to stay.
Callaghan described Sunday's meeting with Hearts as a must-win game and said talk must now be backed up on the pitch.
The reaction follows O'Neill's earlier admission that he had considered his position after a demanding run that included consecutive defeats to Rangers and a loss in Celtic's opening Europa League fixture.
He stayed in the role, and the Hearts match offers another chance to deliver a result.
Before Celtic's win over Motherwell, former Celtic player and Sky Sports pundit Chris Sutton also questioned O'Neill's earlier remarks about his doubts.
O'Neill also drew motivation from Celtic's European history during the visit to the Estadio Nacional in Lisbon, the venue tied to the club's historic European Cup triumph.
He said the connection to Lisbon is something the club should be proud of and that next year's 60th anniversary will be a historical occasion.
He suggested the history could have a galvanising effect on his squad.
Celtic's immediate focus stays on Sunday's home meeting with Hearts as they seek to halt their domestic and European slump.
