Horner has surrendered the Constructors Championship but Coventry City also losing Championship ground to Watford would be adding insult to injury.
The Formula 1 team principal was seeking a third consecutive double title during the 2024 season with Max Verstappen in the car.
The Dutchman duly delivered another drivers' championship, but Sergio Perez's form proved costly in the constructor's standings.
The Mexican trailed teammate Verstappen by a staggering 285 points to finish eighth which meant Red Bull slipped to third overall.
Horner has since been busy in the drivers' market by swapping out Perez for Liam Lawson to hopefully return the team to the top.
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The 51-year-old will be hoping Coventry boss Lampard similarly acts swiftly to conduct any business when the transfer window opens.
Horner's beloved Sky Blues have made an encouraging start under the Chelsea legend, but tougher tests are still to come.
Coventry have won two and drawn once from Lampard's first four in charge with January expected to be a pivotal month in determining what can be salvaged for the remainder of the season.
However, one game stands out above the rest for Horner and that is the visit of his wife Geri Halliwell-Horner's team Watford.
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During an exclusive interview with talkSPORT, the F1 boss told White & Jordan: "It's great to see Frank there.
"I'm gonna go and watch a game in January, Coventry are playing Watford - Geri's a Watford fan."
Spice Girl Geri is one of the many famous celebrity fans of the Hornets, having grown up in the town.
Horner's connection to Coventry similarly stems from his family roots, with his grandfather the purchasing manager at the Standard Motor Company in the West Midlands.
He continued: "My grandad was involved in Coventry City, so we were Sky Blues supporters growing up.
"I'll be going along to have a look and support Frank."
Lampard may be equally as motivated by the task of upsetting high-flying Watford with a familiar figure in charge.
The Hornets were among the pre-season favourites for relegation but sit just outside the promotion spots under Tom Cleverley.
Lampard and Cleverley's England careers overlapped during the latter stages of the former's Three Lions tenure.
Chelsea's record goalscorer also boasts an unbeaten record against his fellow ex-midfielder when they faced each other as players.
Lampard won five and lost none of his seven clashes with former Manchester United, Watford, Wigan, and Aston Villa star Cleverley.
While their touchline reunion may spark a divide in the stands, Horner and Halliwell have finished the year with a united front.
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The Spice Girl supported her husband at Buckingham Palace as he was appointed a Commander of the Order of the British Empire (CBE) by King Charles in the 2024 New Year Honours list for his services to motorsport.
Horner told talkSPORT: "Yeah it was a very special day. Very honoured to pick up an award like that and to be able to share it with your family there.
"The boss himself was handing them out so the King himself was administering ceremonies there so it was a very special day."
During a later chat with talkSPORT Driving, Horner added of his time with 'His Majesty': "He's got an interest obviously in what's going on. He had an awareness of what was going on. So yeah, it was great to have a small amount of time with him.
"It's amazing the coverage and the following that Formula One has. And certainly in recent years, that has just escalated enormously.
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"So yes, it was interesting to catch up on Formula One with a few unsuspecting people that were fans of the sport."
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