The reunion with Chelsea on Monday will probably prompt some short‑term nostalgia at Watford. The last time they met, after all, represented – at least for an hour – probably the apogee of the club’s Premier League project, and for all the drama of their league season so far it is possible to pick out a single moment within this single match at which they were at their brightest and best and after which life has never quite been the same.

At Stamford Bridge in October Watford led 2-1, missed a ludicrously straightforward chance to lead 3-1 and generally outplayed their hosts for much of the game. They were a team bursting with attacking threat in the early days of Marco Silva’s leadership, a more convincing and certainly more compelling side than those produced in the club’s two preceding top-flight seasons by Quique Sánchez Flores and Walter Mazzarri.

But with hindsight the move in the 54th minute in which they sliced Chelsea apart before Richarlison inexplicably put a header wide from six yards seems like a watershed in their season. Two days later Everton sacked Ronald Koeman, started their courtship of Silva, and the fragile foundations that the Portuguese coach had been building began to crumble.

When they arrived at Stamford Bridge Watford had 15 points from eight games and were fourth in the table; in 16 league matches since then they have picked up 11 points, the division’s 19th-best record.

Already their matches had featured an unusual number of late goals but before Stamford Bridge they had always swung results in Watford’s favour, rescuing points against Liverpool and West Brom and earning wins against Swansea and Arsenal. That day they conceded twice in the last three minutes to turn a game they should have won into one they lost 4-2, and it has turned into a damaging habit: since then they have conceded a last‑minute winner against Everton and they led 1-0 in the 86th minute against Swansea and in the 89th minute against Crystal Palace yet somehow lost on both occasions.

It was the team’s fragility and timidity that prompted the owners to remove Silva last month, his period in charge being not so much Jekyll and Hyde as Jekyll and hide. As the season unravelled, the team noticed nothing different about Silva’s approach but there was certainly something different about its effect.

“It’s very easy at the front end of a season to galvanise a diverse group of players around a central cause,” says Jeremy Snape, a former England cricketer and sports psychologist. “Everyone’s fit and motivated and fresh, and pre-season tours are the perfect time to get that shared mind-set, and all the diverse cultures can own that mission and go and get it. Then you get into the challenge of tough games and setbacks, and that early focus gets burned away, and you’re left with a question as to whether you can focus and re-energise. That’s a critical time. Once the season is in full flow it can be incredibly hard to arrest any decline – and if the team’s leadership is also lacking focus, it might be impossible.”

Injuries have certainly disrupted their campaign but the greatest difference between the effective, attacking side of August and September and the limp, brittle version more recently witnessed is surely psychological. The club hopes that the changes made over the last fortnight, including the appointment of Javi Gracia and the arrival in January of a couple of new players, most notably the former Everton, Milan and Barcelona winger Gerard Deulofeu, will lift the mood.

It has at least demonstrated one unexpected benefit of the club’s rotating cast of managers: in the summer Richarlison decided to join Watford instead of Ajax because they had a Portuguese coach with whom he could communicate; in January Deulofeu chose Hertfordshire over unnamed alternatives because by then they had a Spanish coach with whom he could communicate.

Gracia’s focus so far has been on the team’s defensive organisation, while under him Watford are yet to score a goal. Their rambunctious early-season form seems increasingly distant. “There have been different moments in this team and I’m focused on trying to reach the best level and to keep it until the end,” Gracia says. “I know there’s not much time but we have tried, day by day, to work a lot and try to improve the level of the team. We’ll see at the end of the season what this team’s true potential is.”