1) Musetti Top Seed: Lorenzo Musetti has enjoyed another solid year, racking up a 32-27 record and reaching at least the quarter-finals at nine ATP Tour events. The Italian will look to add a third ATP Tour trophy to his collection as the top seed in Sofia, where he reached the semi-finals in 2022.

2) Mannarino On The March: Adrian Mannarino has notched a personal-best 39 tour-level wins this season, a tally that includes title runs in Newport and Astana. The 35-year-old Frenchman will hope to hit 40 and beyond this week in Bulgaria, where he made the last four in 2020 before falling to eventual champion Jannik Sinner.

3) Can Top 30 Stars Claim Late-Season Boost?: Jan-Lennard Struff came within one point of claiming his maiden ATP Tour title in Stuttgart in July. The German has one more chance this year to break his trophy duck when he lines up as the third seed in Sofia. After adding the Cordoba, Kitzbühel and Winston-Salem crowns to his collection in 2023, Sebastian Baez is now a four-time tour-level champion. Can the Argentine make it five in Bulgaria?

4) Former Champion Bautista Agut: After missing nearly three months due to injury from July to October, Roberto Bautista Agut made his return to ATP Tour action in Stockholm three weeks ago. The Spaniard is the only former champion in the field in Sofia, where he claimed the fourth of his 11 tour-level crowns in 2016.

5) Gille/Vliegen Lead Doubles Field: Belgian duo Sander Gille and Joran Vliegen chase their third ATP Tour title of the season as the top seeds in Sofia. Despite narrowly missing out on a Nitto ATP Finals spot, second seeds Nathaniel Lammons and Jackson Withrow have also enjoyed a stellar year, lifting four ATP 250 titles together.