How squad rotation has helped Celtic avoid an injury pile-up

The Scotland international has been the most high-profile casualty so far this season. A knee injury sustained trying to stop a counter-attack by RB Leipzig in early October saw him miss 11 matches. It would have been considerably more had it not been for the one-month World Cup-induced hiatus.

Injury is, of course, part and parcel of all professional sports and something the Hoops are always wrestling with. While no sympathy is asked for nor expected from the rest of Scottish football, the Parkhead side are usually in the hunt for all three domestic trophies, involved in European competition and expected to win every match; there is no let-up in terms of game intensity. 

The Scottish champions have completed 60 matches or more in four out of the last eight seasons. This would have been six out of eight were it not for the coronavirus pandemic.

Squad rotation has been a feature of Ange Postecoglou’s second season and injuries appear to be fewer than in previous campaigns. Are the two connected? Are there other factors at play? Let’s test that perception.

Injury woes

Have Celtic’s injury woes decreased this season? This is tracked using the updates provided by the club on a week-by-week basis. As a backup, the website Transfermarkt also tracks player injury data but is reliant on people providing manual updates so is not always the most accurate.

Sometimes teams are coy about giving information on player knocks. It is sensitive information, after all, and not only from the player’s perspective in terms of their own privacy but in terms of handing a competitive advantage to opposition clubs.

Long story short, the data is far from perfect. All that being said, here are the total number of matchdays missed by first-team squad members per season. If a player misses a game through an injury that is treated as one match lost.

We can see that injuries, in total, were relatively stable under Ronny Deila and then spiked when Brendan Rodgers was in charge.

This is consistent with the injury profile at Liverpool under the Northern Irishman. His training methods were said to be intense and Celtic, winning treble after treble, played a lot of games. 

Injury totals decreased under Neil Lennon before spiking again last season as 'Ange-ball' took hold. The intensity of play under Postecoglou is a key feature, as is the consistent evidence that training is conducted at match tempo on occasion. 

READ MORE: The Celtic shooting trend that could make difference in treble tilt

Last season, as the Australian shaped his rebuild, there were many players utilised but ultimately it was a core of 17 individuals that finished out the campaign. 

To get a clearer picture we need to look at the average number of players missing per match since the number of matches varies from season to season, as does the size of the first-team squad.

In Rodgers’s second season, on average, the Hoops were missing 6.63 personnel each and every match. By the coronavirus hit season of 2020-21, this had decreased to 3.81.

It rose again last season to 5.07 per game under the new manager. The context is football returned to normality in terms of the schedule and calendar. Additionally, the players were adapting to a new boss, new training methods and new playing styles.

What is fascinating is that, this season, the average number of players missing per game is less than three for the first time on record. This is despite a compressed schedule due to the World Cup, plus the intensity of a Champions League campaign.

Game demand

What impact has game demand had in terms of the intensity of the schedule on the players? Here are the average number of days between each match:

This season, with the compression required to fit a World Cup into the middle of the calendar, has seen the fewest number of days per match at 4.52.

This broadly equates to the average number of rest days between matches. The higher this number the better as this means that more time elapses for the athletes between high-intensity matches. The convention within sports science is that players should have at least four days between competitive games. 

The 2019-20 season saw the Hoops go far in Europe on top of an early qualification campaign while also fighting for all domestic trophies. The season was curtailed so the total burden was not as severe but matches nevertheless came along every 4.95 days. 

This season has been even more intense than that. Yet, despite this and also on the back of an injury-hit campaign last season (remember some injuries linger from one season into another), this term has seen a low in injury impact. What can the reason be?

READ MORE: The Celtic Creatives with Alan Morrison - Get it in the mixer!

Rotation

There are now only three players in the first-team squad that were not either signed under Postecoglou’s reign or came through the youth ranks – Scott Bain, Greg Taylor and David Turnbull. 

This means that, largely, the squad is the current manager’s choice and he is comfortable with rotating what he has. Last season this was not the case. Over 40 players made appearances for Celtic and the Australian settled on using only 17 in a meaningful way from the January window close to the end of the season. 

Has rotation increased this campaign? The number of changes to a line-up per match was tracked and this represents the average number of changes to the starting XI per game per season:

The number of changes each manager makes on average per match is usually around three across recent reigns. Under Postecoglou, that has increased to 4.1 this season.

This isn’t a huge difference when we consider the averages but remember there is at least one more player being rotated in and out every single match. Small margins are meaningful in professional sport.

Other factors

The number of rotations increasing may, therefore, be having a positive impact on the overall injury volumes. However, we need to consider other factors.

Firstly, it may be just luck. We are talking about small marginal increases and decreases. Pure fortune may be playing a part in terms of the overall injury picture.

Secondly, it is understood that during Postecoglou's tenure the training equipment and especially recovery equipment - for instance, ice baths - have improved and been modernised. The Australian also brought in his own head of sports science in Anton McElhone, previously of Tottenham Hotspur. Finally, the players are probably adapting to the demands of training and match conditioning under the ex-Socceroos coach.

Summary

This season Celtic’s injury profile is the best it has been in recent times despite playing a lot of matches over a short period. What has evidently increased is the rate of player rotation as the manager has a larger squad which is full of his signings.

In addition, there have been improvements to conditioning equipment and changes in sports science personnel in the background - but never discount the possibility Celtic have just been luckier overall than in previous seasons.

This all said, stalwarts McGregor and Cameron Carter-Vickers did miss chunks of the Champions League campaign and the centre-back position seems to be blighted more than any other this term... so there is always something to complain about.