Chelsea won the Premier League in 2016/17 because they deserved to, there can be no disputing that. Antonio Conte's team set a new English record for wins (30) in a 38-game season, enjoyed a record equalling run of 13 consecutive wins between October and January, and tactically outclassed virtually every other team after adopting an impressive 3-4-3 formation.
They were fortunate too, though. There were no major injuries at any point in the season, allowing Conte to make fewer than 40 cumulative changes to his starting XI over the first 36 games until the title was mathematically guaranteed - the norm for Premier League title winners is usually between 110 and 120.
That and the absence of European football from the schedule, meaning no midweek travelling or extra games, gave Chelsea a significant edge, one they made sure to take advantage of.
As 2017/18 looms, things are different. Champions League football is back, meaning six extra games between September and December - the period in which Chelsea effectively won the Premier League title last season - while as champions they now have an additional target on their back.
Strengthening and adding depth to the squad, especially after the mistakes of 2015 following the club's last title win, is key and is arguably yet to happen this summer - Conte's frustration with the club hierarchy on the transfer front has also been the subject of much negative gossip.
What Chelsea need to move forward and remain ahead, or at least competitive, domestically while also returning to the continental stage is quality and numbers. In Alvaro Morata, Conte has a talented forward with a lot of potential, but he only replaces a proven Premier League striker in Diego Costa, a player seemingly set for the exit with no way back at Stamford Bridge. Chelsea were already too light up front anyway.
Similarly, Tiemoue Bakayoko arrives as Nemanja Matic, an important but perhaps under-praised member of the title winning side, leaves for Manchester United. The 22-year-old powerhouse midfielder comes very highly rated, but arrived injured, may need time to settle and adapt, and notably lacks experience after just a single season as a starter at Monaco.
Antonio Rudiger is another one in/one out signing at centre-back, coming in after the release of club captain and Chelsea legend John Terry. It remains to be seen if the German will be a regular starter or if Conte will stick the Azpilicueta, Luiz, Cahill triumvirate that proved so successful in 2016/17. Either way, Kurt Zouma has also departed on loan so defensive numbers are down.
It was vital that Chelsea strengthened at wing-back this summer. The position on either flank is so crucial to the 3-4-3 system working that the whole formation will quickly fall apart without two players will a very specific skill set. Those players, who must be both defenders and attackers in a way that normal full-backs aren't, can be hard to find and it's not something that can be fudged.
In Victor Moses, a surprising revelation on the right, and Marcos Alonso last season, it worked. The pair were exactly what Conte needed to make the system tick. But on the rare occasions when either was not involved, things were difficult. Cesar Azpilicueta, although a natural full-back and a top class player, does not have the right skill set to be a wing-back and there are real alternatives.
Conte recently admitted he wanted Kyle Walker from Tottenham before Manchester City got there first, while Chelsea were also rumoured to be interested in Danilo, again before he also joined City. On the other side, a seemingly close deal for Alex Sandro has been stalled for weeks.
As things stand there are no back-ups for Alonso - Kenedy has given himself a problem after recent disciplinary issues and is only debatably up for the task after failing to break into Watford's team on loan - or Moses. And, overall, a first-team squad of only 22 players, even if the majority won the Premier League mere months ago, is simply not enough.
Chelsea previously failed to strengthen in the summer of 2015 and it cost them. Only Pedro arrived as an obvious quality addition, with Baba Rahman acquired for his potential more than anything else, while Papy Djilobodji was a deadline day buy at centre-back born out of sheer desperation.
Another factor that characterised the dismal 2015/16 campaign when the club, as reigning champions, initially flirted with the relegation zone before ultimately clawing their way up to 10th place was the form, or lack thereof, of the influential Eden Hazard.
Beset by niggling fitness issues and rushed back to action before he was ready out of desperation on more than one occasion, the Belgian had a nightmare campaign, the anomaly in an otherwise stunning career. He will start this season injured too after suffering a broken ankle while on international duty in June and may not be back in action until late September or October. Without Hazard, Chelsea lack their game changer and risk getting left behind as they did two years ago.
From that point in the autumn of 2015, it was momentum, later to become Chelsea's best friend in 2016/17, that was their worst enemy as one bad result turned into another and another. Even the most ardent 'head in the sand' Chelsea fans cannot help but be a little concerned over what the coming months will bring if nothing else changes.
Several rivals are stronger and the battle for the top four is more competitive than ever. Chelsea may not be looking at something as dire as a another 10th place finish, but a serious challenge to defend the title or even a Champions League berth is now far from a sure thing.