Glenn Whelan has become the latest injury concern for Republic of Ireland manager Mick McCarthy ahead of the Euro 2020 qualifier showdown with Denmark in two weeks' time.
The midfielder was forced off with a hamstring problem just 25 minutes in Hearts' 3-0 loss to Rangers in the Betfred Cup semi-final on Sunday.
McCarthy will definitely be missing suspended captain Seamus Coleman for the must-win clash on 18 November while goalkeeper Darren Randolph is in a race against time to recover from a thigh injury.
Wolves and Ireland full-back Matt Doherty, who will be in line to replace Coleman, went off in his side's 1-1 draw with Arsenal on Saturday, after falling and aggravating a long-standing knee problem, but is expected to to be fit to face the Danes.
So too is Sheffield United centre-back John Egan after coming off during Sheffield United's win over Burnley through illness.
Despite being given a 'farewell game' by former Ireland boss Martin O'Neill almost a year ago, 35-year-old Whelan has re-established himself as a regular under McCarthy and started five of the seven qualifiers to date.
Hearts had lost Whelan to injury midway through the first half as well as Michael Smith just after Rangers grabbed their second goal.
"It was disappointing," said caretaker manager Austin MacPhee.
"We knew everything had to go our way if we were to get a result but to lose Glenn so early - a very important player for us - and then we lost the goal just before half time.
"We lost a goal and also Michael Smith and it was a terrible time to lose a goal, as well as two key players lost through injury."