In January 2022, SPFL approved the use of five substitutes within the 90 minutes of a match at a board meeting.

This had been something that became the new normal during the Covid-19 period but Scotland had reverted to three subs for the start of the 2021-22 season.

Given the depth of the relative SPFL squads, this does appear to give the two largest clubs another advantage over their less well-monied opponents. Both Glasgow giants can afford to have deep pools of quality players.

Against tiring opponents and late into games, more of those quality players can be deployed from the bench.

Celtic scored twice in the last 10 minutes at Dingwall recently to turn a point into three. A 75th-minute goal had been needed to see of Aberdeen on matchday one. Goals also came in the 76th and 82nd minutes against Kilmarnock on Sunday.

Late goals are not unexpected. It is natural for teams to tire and space to open up the longer the game progresses.

Last season, 13 per cent of goals were scored in the last 10 minutes of SPFL matches. For Celtic, that went up to 15 per cent.

It is a very different story at the other end of the pitch.

Here, Celtic conceded only two goals all league campaign after the 70th minute: John Souttar’s late headed winner on matchday one and Dylan Levitt’s long-range wonder-strike at Tannadice the night the title was clinched.

Only five per cent of goals were conceded in the last 10 minutes.

READ MORE: The late Celtic goals that helped propel Ange Postecoglou's side to Premiership glory

Rangers, by contrast, scored 12 goals in the last 10 minutes of last season (also 15 per cent) but conceded three in the same period (10 per cent of their total). Perhaps more remarkably, the Ibrox side scored 31 per cent of their goals (25) in the last 20 minutes of games.

Celtic in particular play a very aggressive high pressing style of football out of possession. There is also an emphasis on restarting play quickly. Joe Hart’s goal-kicks, throw-ins and even short corners are all executed at speed to maintain a momentum of pressure on the opposition.

When you can change half your outfield players, the forward players especially can maintain high pressing and sprint volume knowing they will likely only need to perform like that for 60 minutes or so.

And what of the players substituted in? Do they find it easier to create and score against tiring opposition? Or does it take time to get into a game and its rhythm?

To answer this, we have compared Celtic’s main attacking players from last season and calculated their expected goals (xG) and expected assists (xA) combined as their expected scoring contribution (xSC). These are then compared against the same metrics for their appearances as substitutes.

Celtic Way:

These are small samples, so be aware of that.

The difference column on the far right is that between the player's total xSC and their xSC when coming on as a substitute – both values ‘normalised’ on a per-90-minute basis.

Only Reo Hatate, Daizen Maeda and David Turnbull have xSC’s lower than their overall expected contributions.

Tom Rogic, James Forrest and Mikey Johnston’s numbers were no different whether they come on as a sub or start.

But the majority of Postecoglou’s new signings create much more expected goals and assists coming on as substitutes than they do overall.

Jota, Giorgos Giakoumakis, Kyogo Furuhashi, Liel Abada and Matt O’Riley have xSC over one for their sub appearances.

This doesn’t mean we now think Jota’s best position is on the bench – but that unleashing a fresh Jota against a tiring opponent certainly is effective.

Celtic Way:

Celtic are only three games into the season but there have been calls to replace some of the first XI who have had quieter starts e.g. Furuhashi and Maeda with Abada and Giakoumakis.

While the former pair’s respective starts to the season have not been as spectacular as O’Riley’s or Jota’s in particular, this tends to underestimate the ‘softening up’ that takes place from those starters that provides the platform for the substitutes to come on and be effective later in the game.

Celtic must be a horrible team to play against. Like defending a swarm of angry wasps. The defence never gets a rest and there are always players snapping at you to win the ball back. Then Furuhashi gets tired and on comes the rambunctious Giakoumakis to rough you about.

Such an approach is mentally and physically draining. Celtic’s third goal resulted from Giakoumakis winning the ball back, aided by Greg Taylor, in a high press in the 92nd minute against a very tired County player.

The five-substitutes rule will arguably ultimately make the league less competitive in terms of the gulf between those that can afford very strong benches and those less monied clubs.

In particular, given the style of play Celtic adopt and their financial advantage over the rest of the league, they can now play high-intensity football for near on the full 90 minutes.

The substitutes they bring on will invariably be strong and, as we have seen, contribute even higher expected goals and assists than those they replace.

Not many domestic opponents will be able to live with that.