In tomorrow’s Old Firm match, there will be key individual battles happening all over the pitch.
However, perhaps none will be as influential as that between Daniel Candeias and Emilio Izaguirre.
Barring a couple of suspensions, Candeias has been a near ever present under Steven Gerrard.
It was his clever header that released Alfredo Morelos to open the scoring against Hibs on Saturday.
In addition to his creative spark, more goals have been added to his game this season.
He has netted four in the league, including match-winners at St Mirren and at home to Livingston, as well as one in the Europa League group stages.
His role becomes even more important tomorrow as he is likely to be up against a stand-in.
Kieran Tierney looks unlikely to feature, having missed the last four matches with a hip injury.
Izaguirre a weak link for Celtic
In his place should come Izaguirre. The Honduran is in his second spell at Celtic and boasts experience, but has struggled to capture his best form since returning to Parkhead.
He was substituted at half-time by Brendan Rodgers in the 4-3 win over Aberdeen. Winger, Jonny Hayes, replaced him for the second period.
While Izaguirre’s experience should be enough to ensure he is reinstated tomorrow, he is vulnerable.
Candeias is excellent at hassling and harrying opponents. On top of that, he needs to ensure he looks to beat his marker at every opportunity.
If he can win this key battle on the right flank, it is a route to the heart of the Celtic defence and quite possibly, an Old Firm victory.