It will not be known for a day or two how long the knee injury - inflicted by Southampton's debutant French defender, Patrick Colleter - will keep Poyet out, but, as he missed eight months of last season with cruciate ligament damage in the same area of his leg, the knock was causing concern on Saturday night.
"We'll miss him if he has to be out because he's on fire at the moment," Graham Rix, Chelsea's first-team coach, said. Poyet will be especially missed if he cannot play against Manchester United at Stamford Bridge tomorrow.
"We showed at Old Trafford [in the recent 1-1 draw] that we can match United but they've got a very good record at Stamford Bridge," Rix said, but would not be drawn on the significance of tomorrow's game to both sides' title prospects. "It is a big game," he said, "but, win or lose on Tuesday, it doesn't mean we're going to win or lose the championship."
Whatever Rix's public pronouncements, there can be little doubt that what happens tomorrow will be, if not crucial, then significant in indicating the championship potential of the first and second-placed clubs. Chelsea hope to welcome back Marcel Desailly, Roberto di Matteo and Graeme Le Saux (absent on Saturday due to the birth of his daughter on Christmas Day), and their participation can only make a side brimming with quality even stronger.
Saturday's first goal exemplified the class of their mercurial Little and Large pairing, a deft run by the diminutive Gianfranco Zola down the left ending in a cross met by the towering Tore Andre Flo and slotted home with the merest pat of the boot.
Bjarne Goldbaek was a powerful creative force in midfield and every time Franck Leboeuf took possession he tore forward like a steamroller through a field of matchstick men. If any man in Blue looked a liability it was Ed de Goey in goal, but even his occasional flappings were never likely to be punished by the Saints.
Rix gave notice that his side are not merely a bunch of mercenary foreigners on a lucrative jolly, but a committed unit consisting of internationals on one hand and home-grown youth-programme talent, such as Jody Morris and John Terry, on the other. "World Cup winner [Leboeuf] or 17-year-old boy [Terry], they're all pulling in the same direction," he said.
As for Southampton, their visitors on Saturday were just the latest side to have beaten them this season. They now face two vital relegation matches, starting today at fellow strugglers Nottingham Forest, while Charlton will be the next League opposition at The Dell on 9 January.
The signs were not all bad against Chelsea - Matt Le Tissier looked sharp and committed before having to leave the field with a calf pull after 25 minutes, Colleter made an assured debut, and the Moroccan Hassan Kachloul showed potential with several runs - but the time has come to turn potential to points.
Goals: Flo (20) 0-1; Poyet (48) 0-2.
Southampton (4-4-2): Jones; Colleter, Lundekvam, Monkou, Hiley; Kachloul, Palmer, Le Tissier (Ripley 25; Basham, h-t); Oakley (Dodd, 82); Ostenstad, Beattie. Substitutes not used: Bridge, Stensgaard (gk).
Chelsea (4-4-2): De Goey; Ferrer, Duberry, Leboeuf, Babayaro; Petrescu, Poyet (Terry, 73), Morris, Goldbaek; Zola, Flo (Nicholls, 83). Substitutes not used: Forssell, Myers, Hitchcock (gk).
Referee: D Elleray (Harrow). Bookings: Southampton: Colleter. Chelsea: Morris, Babayaro.
Man of the match: Zola.