It's the final week of regular ATP World Tour action before next week's season-ending Tour Finals, so this represents one last chance for most to bag a trophy or improve their ranking heading into the off-season.
The tournament has taken place at the Sofia Arena every year since 2016, although it was initially dropped from the 2023 season before being reinstated after the Tel Aviv Open was cancelled.
As the rescheduled event falls between the Paris Masters and the Tour Finals, there is a lack of star quality on display, with Italian world no.22 Lorenzo Musetti the highest-ranked player in the draw.
Jack Draper to win @ 6/1
Musetti might be the top seed, but the Italian is on a collision course for a second-round clash with Jack Draper, and it's the highly-rated Briton who is preferred for a Sofia outright wager.
Draper is ranked 91st in the ATP Tour rankings, but that doesn't tell the entire story for the 21-year-old Londoner, who was forced to miss three months in the middle of the season due to a shoulder injury.
That injury, sustained at the French Open, ruled Draper out of the entire grass season and a good portion of the North American hard-court season, causing his ranking to plummet from a career-high 38th to 123rd by mid-August.
However, Draper returned to action in encouraging style, winning three matches at the US Open, including a straight-sets win over Hubert Hurkacz, and there's no denying that he has the talent to capture 250 Series titles on the ATP Tour if he stays healthy.
Sensibly, Draper has eased himself back into post-US Open action, reaching the final of a Challenger Tour event in Orleans, France, at the beginning of October, then doing likewise in Bergamo last week, while there was no shame in losing a close match against world no.13 Alex de Minaur in the opening round in Japan between those two efforts.
At the end of a frustrating season, Draper would dearly love to sign off with a first ATP World Tour title, and, should he defeat Maximilian Marterer in round one, there is every chance he can see off Musetti, who has won one of his last five matches.
From then on, he would have to be considered one of the favourites to take the title.
Pavel Kotov to win @ 16/1
Pavel Kotov was denied a first ATP Tour title when going down to Gael Monfils in three sets in the Stockholm Open final last month, but the improving Russian has the tools and the draw to go one better in Sofia.
Kotov saw off some solid opposition in Stockholm, beating Christopher Eubanks, Lorenzo Sonego, Tallon Griekspoor and Miomir Kecmanovic before falling short against La Monf, hitting a new career-high 81st in the aftermath of that event.
The 24-year-old starts his campaign against Bulgarian wildcard Alexandar Lazarov, ranked 709th in the world, and then he'll face Sebastian Baez, who has been in dismal autumn form, winning just two matches in five tournaments.
Veteran Adrian Mannarino, the highest-ranked seed in the bottom half, has also struggled since winning the Astana Open, so there's not much for Kotov to fear.