LAST summer was expensive in more ways than one for Celtic. The club’s bank balance took a hefty hit as the Parkhead club sanctioned a whole bunch of multi-million pound acquisitions to beef up Neil Lennon’s squad for their ultimately doomed title tilt. But it proved costly on the park, too, as new signings failed to gel and left the club’s bid for ten-in-a-row in tatters by the turn of the year.

Let’s have a quick roll call. Vasilis Barkas was brought in for £4.5million from AEK Athens and now holds the dubious honour of being the most expensive back-up goalkeeper in the history of Scottish football. Albian Ajeti was recruited from West Ham for a cool £5m and after an initial promising spell, has scored just once since September. And the less said about Shane Duffy, for whom the Premiership’s runners-up-in-waiting paid £2m for a season-long loan, the better.

David Turnbull is the only new face to have pitched up in Glasgow’s East End who can be said to have been a success and even then, there’s an argument to be made that his move should be associated more with the previous summer’s window when the Motherwell midfielder watched a move collapse after an issue was flagged in his medical.

Barkas, Ajeti and Duffy have all failed to make the grade this term, and the unhappy trio are three of the most extravagant bench-warmers in the country. But there’s another man who arrived this summer – one who has just about nailed down a starting spot – who should really be joining them.

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When Diego Laxalt was signed from AC Milan, Celtic fans were understandably excited. After all, the left-back is a Uruguay internationalist. Heck, his move to the San Siro was in the eight-figure region. But while Laxalt has received significant game-time this season, the stats suggest that he really shouldn’t have.

Laxalt, of course, is vying for a place in the starting XI with Greg Taylor, the full-back Celtic signed from Kilmarnock in 2019. Supporters have been reluctant to embrace the Scotland internationalist – and let’s face it, a 23-year-old lad from Ayrshire isn’t quite as sexy a name as an AC Milan defender – but his exclusion from the first team is becoming harder and harder to justify.

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Let’s start with the basics: first and foremost, defenders need to defend. Their top priority has to be keeping the round white thing out the net and perhaps unsurprisingly, Taylor – a first-class graduate of Steve Clarke’s school of hard knocks – has the edge over the Uruguayan in this regard.

The two left-backs attempt roughly the same amount of defensive duels per game, but it is Taylor who wins almost 10 per cent more of them. The reverse is true when we look at aerial duels – in this instance, it’s Laxalt that has a 10 per cent lead on the former Killie player. Although, it must be said, neither are particularly proficient in the air – both lose more aerial duels than they win. Truthfully, it’s not the most important stat for a full-back.

The two players are just about tied on the number of interceptions they complete per game but there is one metric that highlights Laxalt’s lack of defensive nous: the 28-year-old gives away 2.29 fouls per 90 minutes played. Taylor, by contrast, gives away just 0.81.

So what does this tell us? Probably what most fans could deduce via the eye test – that Taylor is the more natural defender of the pair. But of course, that’s only half of the job required of a modern-day full-back. Their attacking contributions matter too, and this is where we see Taylor’s true value.

Laxalt is the better dribbler of the two, of that there’s no question. The Milan loanee’s runs forward are successful 69 per cent of the time – a fine return – compared to Taylor’s bang-average 57 per cent. It’s a similar story when we look at progressive dribbles (runs where the ball is advanced at least 10 metres up the park) per 90 minutes, with Laxalt averaging 3.3 to Taylor’s 2.7.

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The big difference lies within the two players’ final ball. Laxalt, for all his skill with the ball at his feet, is simply wasteful in the final third. He attempts four times as many shots per game as his rival, despite only scoring once this season. Taylor attempts far more crosses (5.8 compared to 3.4) and with good reason – 37 per cent of his deliveries find their intended target, a huge increase on Laxalt’s paltry 22 per cent.

As you’d expect, this discrepancy is borne out when we look at the Premiership’s assist tally. Laxalt, with almost 1,300 minutes of league football under his belt this term, is yet to register an assist. Taylor, meanwhile, has four in 1,650 minutes. A cursory glance at the duo’s key passes (a pass that leads directly to a shot) tells the same story – Taylor creates more than three times as many of these opportunities than Laxalt does in any given league game on average.

However, assists don’t paint a full picture. In order to successfully tee up a goal for your team-mate, you need them to put the ball in the back of the net. It’s out of your hands. You could give them the easiest chance in the world to bury and they might somehow end up scooping it over the bar from a few yards out. Equally, if a goalkeeper was to play a short pass to a defender who went on to beat the entire team and score, then the goalie would get the assist.

These examples serve as a useful reminder that a player’s assist tally isn’t necessarily representative of their creative output. In the former scenario, the chance has an extremely high chance of going in. In the latter, the odds drop to about as close to zero as you can get.

Thankfully, we have a solution: Expected Assists (xA). This metric works in much the same way Expected Goals (xG) does: the odds of any given chance being converted are calculated and represented as a number between 0 and 1. A really good chance might have an xA of 0.6, for example, while a speculative pot-shot from the halfway line would be around 0.01 (meaning it has a one per cent chance of going in).

When we examine Taylor and Laxalt’s xA per 90, we see can see why Taylor is by far the superior option. The Scot has an xA per 90 of 0.24, while Laxalt is lagging way behind on 0.06. Or to put that another way – based on the quality of chances that he creates, Taylor can expect to register an assist every four games. Laxalt, meanwhile, should grab one every 16 matches.

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Taylor’s xA isn’t just good; it’s superb, particularly for a full-back. David Turnbull (0.36), Ryan Christie (0.3) and Tom Rogic (0.26) are the only players on the books at Celtic Park who create higher quality chances more regularly than Taylor. In fact, Taylor’s xA per 90 is up there with the best in the entire league. He has the joint-fifth highest xA per 90 of any player in the league and statistically, his creative output is identical to that of James Tavernier (also 0.24).

The Rangers skipper has nine assists to his name and is generally regarded as the most creative ‘defender’ in the league but according to the data, Taylor is matching him pound-for-pound when he gets the nod. It might be a little jarring to read but the numbers are unambiguous and do not lie: per 90 minutes played, both Tavernier and Taylor create the same quality of chances at the same rate.

There is a reason for this, however. With Laxalt generally being first pick this season, Taylor often misses out for 'bigger' games. He's only played 96 minutes of league football against the rest of the top four - Rangers, Hibs and Aberdeen - this season, and could be accused of 'stat-padding'. Essentially, this means that his numbers have been beefed up by playing against inferior opposition. This is undoubtedly true but still, the numbers Taylor posts when he does play are remarkable for a left-back.

This is the crux of the matter. Celtic have a player who is significantly younger, who won’t be leaving in the summer and who more of a natural defender than Laxalt. He doesn’t offer the same attacking verve when he drives at opposition defenders but his creative output – the thing that truly matters for a full-back in an offensive system – is lightyears ahead of the Uruguayan and makes Taylor one of the league’s top performers in this regard. Celtic simply cannot afford to sideline him any longer.