Chelsea have dropped more points from winning positions at home than any other team in the Premier League this season.

It is a trend manager Enzo Maresca concedes is "not random" and he wants "to understand why".

It is especially frustrating for Chelsea as fast starters at Stamford Bridge, having scored first in eight of their past nine home matches. However, they have also dropped 11 points from winning positions at home - more than any other Premier League club.

In total, Chelsea have surrendered 13 points from winning positions home and away, which equals the gap to league leaders Arsenal.

Maresca's shift in tone on the issue followed Saturday's 2-1 defeat by Aston Villa.

Substitute Ollie Watkins scored two second-half goals to leave Chelsea 10 points behind third-place Villa.

Speaking to BBC Sport before Tuesday's visit of Bournemouth to Stamford Bridge, Maresca said: "When something continues to happen, it's not random.

"So we need to understand why. No matter if we are winning, drawing or losing, we concede a goal, we lose a little bit of control. So we need to understand the reason why."

As Villa manager Unai Emery's changes swung the game in their favour, Maresca's substitutes made little impact.

Star attacker Cole Palmer reacted furiously to being taken off in the 72nd minute for 18-year-old Estevao Willian, while the decision to withdraw Marc Cucurella drew criticism - though it was later revealed that the Spaniard had a potential hamstring issue.

Maresca's substitutions have faced scrutiny before, notably in defeats with 10 men against Manchester United and Brighton earlier this season. Atalanta forward Charles De Ketelaere even suggested they "drop" in the second half after his side came from behind to beat Chelsea in their Champions League game in Italy earlier this month.

While Maresca's changes have occasionally worked, it has usually been when resting key players. Against Nottingham Forest and Brentford in the Premier League and Cardiff City in the Carabao Cup, he rotated heavily but ultimately relied on star players to secure wins.

This has sparked a chicken-and-egg debate: some blame the lack of quality on the fringes of the squad, while others question Maresca's handling of certain players.

Asked about the issue by BBC Sport, Maresca smiled before replying: "No, I think it's in general."

That guarded response came after a defeat defined by substitutes.

Villa's quintet of Watkins, Amadou Onana, former Chelsea loanee Jadon Sancho, Lucas Digne and Lamare Bogarde, had an average age of over 26.

Chelsea, meanwhile, made four changes - Estevao Willian, Jamie Gittens, Liam Delap and Malo Gusto - with an average age of under 21.

In terms of attacking impact, Estevao has delivered five goals and an assist since moving to Stamford Bridge, but injury-hit Delap has scored just once, as has Gittens, albeit having also delivered five assists in all competitions.

"It's probably how we can improve after we concede a goal, to manage the game a little bit better, in terms of experience game after game," says Maresca.

Chelsea rely on youth, and have had minimal impact from their changes in the Premier League this season.

The average age of their starting XI is 24 years and 219 days, while substitutes average 21 years and 349 days - both are the youngest in the league.

Alongside Arsenal, Chelsea make the earliest changes, averaging their first substitution at 48 minutes, often at half-time. Despite this, their substitutes have contributed only three goals and one assist in the league this season.

Maresca appears ready to move on from saying "many people" caused his "worst 48 hours" following their 2-0 win over Everton earlier this month.

His remarks were widely interpreted as criticism of a perceived lack of support from Chelsea's hierarchy after successive defeats by Leeds and Atalanta.

Maresca insists he is doing a good job with the Premier League's youngest squad, with Chelsea setting Champions League qualification via their league position as the minimum target.

He is encouraged to rotate and use the full depth of his squad, and no team has made more starting XI changes than Chelsea's 146 across all competitions.

Yet Maresca has admitted players like Andrey Santos are not yet at the level of regular starters such as Moises Caicedo.

Chelsea have slipped below Liverpool into fifth and risk being dragged into mid-table, sitting just seven points above 15th-placed Bournemouth before Tuesday's game in west London.

Home form is a growing concern. Chelsea have not won successive home matches and have already lost three league games at Stamford Bridge, as many as they did in the entirety of last season.

Asked about Chelsea's target, Maresca said: "The last game doesn't reflect a 10-point difference between us and Villa. So we need to be confident and to think that we can go close again to those ahead of us."

Injury concerns remain. Cucurella is a doubt, Jorrel Hato is still out, and both Palmer and Reece James will be assessed during a busy fixture period. Wesley Fofana, however, is fit and was only rested against Villa.