The World Cup qualifier at home to Germany in October could give a good indication of how Northern Ireland might line up against a leading nation without Bradley.
After a starring role in the win over Slovakia in the previous match, he picked up a yellow card which ruled him out of the Germany game through suspension.
On that occasion, it was Spencer who was tasked with filling in at right-back as Hume retained his spot in the centre of a back three.
The step up in opposition definitely played a role too, but Northern Ireland were certainly less dynamic than against Slovakia, as they missed the drive Bradley offers going forward.
Digging into the numbers, Spencer stacked up well against the Liverpool man. Bradley won four fouls against Slovakia, while Spencer won two against Germany.
Those stats are flipped for fouls conceded, and Spencer made 24 passes with a 67.7% success rate, while Bradley had 52.9% success rate from 39 attempts against the Slovaks.
In the BBC Sport player rater, where BBC Sport readers can have their say on the game, Bradley was top at 8.90 against Slovakia, while Spencer was at 6.68 against Germany - when Ballard was the highest with 7.79.
Albeit away from home, Northern Ireland will be hoping for a similar level of performance to the Germany game - just with a different result.