Celtic manager Brendan Rodgers pinpointed reaching the Europa League as the target to show his side had progressed in Europe.
That goal was achieved from a punishing Champions League group stage in which the Scottish champions lost five of their six games.
The 3-0 away win over Anderlecht was a signal that Celtic had improved.
But that notion was completely undermined by the manner of the 1-0 home defeat to the Belgian side.
Domestically, Celtic are streets ahead of the rest of the Premiership, although not quite as dominant as last term.
- Zenit favourites against Celtic – Rodgers
- Analysis: Zenit strength poses threat to Celtic
- Celtic v Zenit – team news & preview
Europe has proved an exceedingly tough examination. Financial disparity is clearly a vital factor but is not everything. Evolution can still be achieved.
Are Celtic better equipped to compete against Zenit St Petersburg when the Europa League enters the round of 32 stage on Thursday?
‘We need to be better’
Rodgers’ side were always up against it when facing Paris St-Germain and Bayern Munich. The true measure was the Anderlecht double-header, which threw up some interesting home truths.
Following the home loss to the Belgians, Rodgers said: “Some of our players have a long way to go before they can call themselves players at this level.
“We need to be better, but we’ve shown that we can be. We have a lot of work to do before we can affect that level.”
It was the manner of defeat that was concerning. Celtic were a distant second best. Technically inferior, limited in terms of their movement and lacking threat.
So, in what areas are Celtic better?
“We need players that can make the difference and not just domestically,” Rodgers told BBC Scotland last month. “If we’re going to do anything in European football, we need extra quality in our squad.”
Europe was the focus for signing targets.
Supporters often demand big-money singings and Celtic were in a position to spend. It is not a simple as that though as the right player has to be available.
Marvin Compper was recruited but is ineligible. Scott Bain was brought in as back-up on account of Craig Gordon’s injury. Jack Hendry came in from Dundee and has promise but no European experience.
Charly Musonda, on an 18-month loan deal from Chelsea, has been heralded as the creative spark that was missing. He was courted by a number of clubs but has little first team football under his belt.
Is Rodgers looking to the 21-year-old Belgian as the missing link for this double-header so early in his Celtic career?
On the recruitment front, Celtic appear to be of a similar standard now as they were when they lost to Anderlecht. When you account for a long injury list, they may well be weaker.
Case for the defence
Celtic had the worst defensive record in the Champions League group stage, conceding 18 goals – an average of three per game.
Given the strength of opposition, some of that can be mitigated when compared to teams performing in weaker sections.
However, defence remains a considerable concern.
Dedryck Boyata is likely to be sidelined with injury. Dorus De Vries will start in goal, having limited appearances and only one European start, a 7-0 defeat in Barcelona.
Kristoffer Ajer’s European experience is limited to facing Lincoln Red Imps last season, this term’s home qualifier against Rosenburg and away to Astana. The teenager has shown promise but needs to perform to the top of his game against Zenit.
Jozo Simunovic was far from convincing against Partick Thistle on Saturday. He sold the opener with a poor back-pass then casually conceded cheap possession before Conor Sammon outmuscled him to score the visitors’ second.
Kieran Tierney needs no introduction. An outstanding player who Celtic will need in defence and attack.
The value of a clean sheet in this home leg is immeasurable. The defensive performance will have to be light years ahead of the error strewn display against Thistle or Zenit will profit.
Celtic Park effect
Infamous European nights at Celtic Park are fading from memory. The last home win in either the Champions League or Europa League came against Ajax in October 2013.
Aside from a thrilling 3-3 draw with Manchester City last season, Celtic have struggled on home turf lately.
That night, Moussa Dembele was outstanding, with two goals and a robust energy that has been missing of late.
The entire team showed intensity, desire, focus and skill. They shrugged off any suggestion of being inferior and gave City an almighty fright.
That is the level of performance needed against Zenit. Shackles off, get the crowd off their seats and make the stadium the intimidating cauldron it can be.
To do that, Celtic need to be positive and believe they belong at this level.
Scottish clubs have long bemoaned entering European qualifiers while effectively still in pre-season.
Zenit come into this tie having not played competitively in over two months. The boot is firmly on the other foot.
Should a high-energy approach be Celtic’s game plan? Match-fitness may tell. Creative players must shine and generate pressure.
James Forrest is having the season of his career. In contrast, Scott Sinclair looks lacking in confidence. His goal return remains strong but he is not the same player as last season.
As one of Celtic’s main threats, Sinclair needs to perform for his side to prosper.
A clean sheet would be most welcome, as would some sort of advantage. No easy task.
While making Zenit favourites, Rodgers is demanding progress at this level. If Celtic go through they most certainly will have proved that they are on the right track.
If they struggle, particularly in the home leg, then a re-evaluation of Celtic’s European ambition may have to be undertaken ahead of next season.
By then, domestic dominance will not be enough.