Tottenham face Celtic on Saturday afternoon in Helsinki in what will likely be a stern test of their pre-season preparations.
Spurs enjoyed a successful pre-season tour of North America, winning twice and drawing once while Celtic have played three competitive matches already as they seek to qualify for the Champions League.
Five of Spurs' World Cup stars rejoined training on Wednesday having missed the tour but are unlikely to be risked so soon after returning.
In each of Spurs' matches so far, manager Mauricio Pochettino has deployed his players in a 4-2-3-1 formation while generally rotating through most of his squad. He has mixed youth players with the more seasoned players and avoided picking a full-strength lineup at any point.
It seems likely that he will continue with the same setup but we will get a glimpse into Pochettino's thinking regarding the first team for next season.
When Pochettino picked Aaron Lennon, Christian Eriksen and Erik Lamela as an attacking line behind Roberto Soldado against Toronto FC, it looked a little unwieldy but was extremely effective. The versatility of Eriksen and Lamela meant that they could rotate roles, alternatively moving into the No. 10 and wide positions. Lennon was surprisingly effective as he buzzed around the two, creating trouble with his pace and helping to unsettle Toronto's back line.
Eriksen's place is the most under threat should Pochettino return to his favoured 4-3-3 so he needs to impress his new manager. He is not in any real danger of being dropped after his impressive debut season but his preferred role doesn't exist in a 4-3-3 so he must take this opportunity to show his versatility.
Emmanuel Adebayor missed the tour with malaria and he has now returned to training. Pochettino will likely hand him his chance after half-time but Soldado should retain the starting role. The Spaniard was quiet in North America but he impressed with his build-up play, assisting Lennon's goal against Chicago and Lamela against Toronto.
Behind Spurs' attacking quartet, the defensive midfield proved an effective foundation against their MLS opponents and Etienne Capoue was key to that solidity.
The Frenchman struggled with injury last season and faces stiff competition for his place (even if the touted arrival of Morgan Schneiderlin doesn't happen) but he has impressed in pre-season. A tough battle against Celtic's aggressive midfield could leave him as the front-runner for the defensive-midfield place.
Alongside Capoue, Ryan Mason and Lewis Holtby have shared the more technical role.
Holtby was as enigmatic as ever on the tour. He scored a lovely headed goal against Seattle and assisted Harry Kane's opener against Chicago. His engine, never really in question, makes him a reliable and effective presser which is crucial to Pochettino's system. Despite all that, he was lazy and careless in possession throughout the tour and, with the World Cup stars ready to return, Holtby needs to impress.
Sandro also missed the tour and could feature alongside Capoue if Pochettino thinks Celtic's aggression warrants an additional midfield enforcer. Like many of the squad, Sandro is playing for his place.
Spurs' back line has been largely a mix of youth and experience so far in pre-season but it's time for Pochettino to unveil his first-choice back line. The real question is whether Milos Veljkovic has done enough to keep his place.
It seems more likely that Michael Dawson will retain his place and Younes Kaboul will return. Both Dawson and Kaboul are likely competing for the one open place in Spurs' back line. Kyle Walker and Ben Davies are certainties at right and left-back respectively while Jan Vertonghen is virtually assured of his position as one of the centre-backs. Despite the rivalry between Kaboul and Dawson, the two will likely line up together against Celtic.
It will be interesting to see how Pochettino shifts his formation as he reintroduces the World Cup players. The return of Mousa Dembele and Nabil Bentaleb could allow Pochettino to shift to his preferred midfield three.
Spurs' squad isn't really built to play Pochettino's Southampton-style 4-3-3 but if he is keen to return to that style, the addition of players like Nacer Chadli and eventually Paulinho, will better facilitate it. Paulinho is well suited to playing as one of the wide central midfielders in a three-man midfield. It allows him to assist in pressing and build-up while getting forward to help create overloads in the final third. The shift to a three-man midfield could be the key to Paulinho's Spurs career really taking off.
Chadli is another whose Spurs career stalled in his debut Premier League season and he would benefit from a formation shift. As a wide forward, Chadli really didn't fit in for Spurs last season. He struggled in build-up and as an attacking weapon. He lacks the pace to play as a genuine winger but with his strength and shooting ability, he is suited to play on the left of an attacking trident. With experience as a centre-forward, he can also drift inside to help Soldado.
Celtic will provide a tough opposition for Pochettino's nascent Tottenham squad. Spurs are still learning the new style of play and, while they have enforced the pressing system admirably at times in pre-season, they have also drifted through parts of each of their matches so far. Celtic are reeling from their calamitous 4-1 defeat to Legia Warsaw in the third qualifying round of the Champions League. With their exit from Europe all but confirmed, some of their players may take this opportunity to put themselves in the shop window.