THE road to recovery has been a long one for Celtic striker Leigh Griffiths. The 29-year-old missed the majority of the previous campaign after taking time away from football to deal with off-field personal issues, with some fans fearing they would never see the Scotland internationalist play for the Premiership champions again.

The path back to first-team football at Parkhead has been an arduous one for Griffiths to navigate, with the forward only becoming a regular under Neil Lennon since the turn of the year. After being primarily limited to cameo appearances off the bench for the first half of the season, Griffiths has since forged a strong partnership alongside Odsonne Edouard at the head of Lennon's new-look 3-5-2 formation.

The goals have been flying in since and right on schedule, too. With Scotland potentially 180 minutes away from ending the national team's 22-year wait to reach the finals of a major tournament, Griffiths' return to form could prove crucial ahead of this month's double-header to reach EURO 2020.

His hat-trick against St Mirren at the weekend was the first recorded by the former Hibs, Wolves and Livingston man in four years as Griffiths appears to have recaptured his best form. But when we dig a little deeper into the numbers that he has been posting, there is an argument to be made that the striker is playing as well as he ever has for Celtic.

The graphic above outlines Griffiths' performance in domestic competitions in key metrics for a striker and the results make for impressive reading. His goal rate of 0.88 goals per 90 minutes in Scottish football this campaign is the second-highest ratio he has achieved in the last five seasons, and he is laying on more goals for his team-mates (0.35 per 90) than all bar one of the last five years (Griffiths was assisting 0.42 goals per 90 in 2016/17).

Curiously, the striker's average number of shots per game this season has decreased from his usual tally - Griffiths normally averages over 5 per 90 minutes but that has fallen to 3.7 this campaign - but his efforts tend to be more accurate these days. The Scotland internationalist is hitting the target 47.6% of the time; this was only beaten by his rate last year (60.9) and is marginally lower than in 2015/16 (47.8).

Similarly, Griffiths is becoming a more creative outlet in the final third. Key passes measure how many shots a player tees up for his team-mates - a shot assist, if you like - and once again, Griffiths' return this season in this area is up there with the best he has produced in the last five years. Only last season, when he featured as a bit-part player for obvious reasons and so we have a small sample of data to draw from, was he setting up more chances for his side.

When we examine Griffiths' expected goals (xG) and compare that to his goals scored, we can see just how potent the forward has been in front of goal this season. In essence, if a player's goals scored eclipses their xG then they can be said to be overperforming; they are converting opportunities that, statistically speaking, they should be missing based on probability.

As we can see, Griffiths has outperformed his xG in four of the last five seasons: only in the previous campaign did he underperform and obviously, there were more important factors at play than what he was doing on the pitch.

But Griffiths' xG differential this season is truly remarkable. With a surplus of +0.31, the Celtic striker is essentially scoring an extra goal every three games that he shouldn't be. This is comfortably the highest tally the 29-year-old has ever produced in a Celtic shirt. The next-best season was in 2016/17 where Griffiths' xG differential sat at +0.17 - an impressive return, but still only half as good as his performances in front of goal this season.

Given his recent off-field difficulties, few neutrals would begrudge Griffiths' return to form, especially if he can maintain his level of performance for Scotland later this month. And while recent displays have certainly been encouraging for Celtic supporters in this regard, the underlying data is unambiguous. Griffiths isn't just back: he's more deadly than ever.