Doubts about their ability to sustain a serious championship challenge this season have always concentrated more on Vialli's controversial rotation of players than on whether he can end up producing a rounded team with the stamina of mind and body to go with their undoubted talent.
No result had been more persuasive than the 2-1 win over the most durable side in the Premiership, Aston Villa, at Stamford Bridge during the week.
That significant victory had a lot to do with the fact that Vialli himself started his first Premiership match since the opening day of the season and, until tiredness took its toll, led the front line superbly. It was also a result that cast doubt on the theory that Chelsea are only a side to be reckoned with when Dennis Wise escapes suspension long enough. He was left on the bench against Villa, but returned yesterday just before starting another enforced rest.
Vialli omitted himself yesterday, allowing the winning goal-scorer against Villa, Tore Andre Flo, to start alongside Gianfranco Zola up front, but injury meant that Marcel Desailly was missing from the back, so Michael Duberry made his 100th appearance.
Curiously, Chelsea, usually the most cosmopolitan of teams, started with more British-born players than Derby. Chelsea's choice of team suggested that they had in mind Wednesday's crucial test against Manchester United, but in a positive start they almost took a third-minute lead when Duberry headed on Wise's corner and Tony Dorigo was fortunately placed on the goalline to block Bernard Lambourde's attempt. That seemed to be indicative since Derby took 12 minutes to raise a fully supported attack.
Chelsea's confidence was justified in the way they appeared to be using the defensive qualities of their midfield to quash any danger, but against set-piece threats they were less composed. An early corner caused them problems and a 26th-minute free-kick left them a goal down and looking considerably less in control.
Wise had bustled into one of those bristling interceptions on Darryl Powell that gave the referee no choice but to give the free-kick against him.
Horacio Carbonari cracked the kick from outside the penalty area and Ed de Goey suffered the goal-keeping night- mare of seeing the ball deflect off Lambourde before passing him. If only for some splendid individuality from the gangling Paulo Wanchope, Derby deserved to have sight of their first home win since 19 September. Carbonari's third goal in five matches was greeted joyously by the home fans who have been badly deprived of goals at Pride Park this season. Not that Derby created many more goal chances in the first half. Meanwhile, Chelsea always brought crowd-silencing anticipation when Flo or Zola weaved or darted into the Derby penalty area, or when Gustavo Poyet drifted in virtually unseen.
Flo, who this season has often been frustrated by being under-used, again made a strong case for permanent inclusion when, after 54 minutes, he cleverly, almost derisively, made instant contact with a neatly transferred ball sent forward by Graeme Le Saux and relayed by Jody Morris. Flo finished by lifting the ball over the plunging Mart Poom.
Within another three minutes the visitors regained the dominance of their opening efforts. This time it was Poyet who showed impressive self- assurance, slamming in a low and unstoppable shot from a few paces outside the penalty area.
Once Chelsea had secured that sharp comeback and had watched in relieved astonishment as Wanchope controlled Stefano Eranio's cross into the goal area but failed to get the better of De Goey, they attempted to close down the game. Since Derby had deteriorated considerably after their most promising period in the later stages of the first half, that did not present much of a problem. Derby made three simultaneous substitutions hoping that Kevin Harper and Dean Sturridge in particular could give attacking support to Wanchope, but in taking off Carbonari they looked as if they might have deprived themselves of their most likely goalscorer.
As it was, Sturridge and Harper did indeed come to Derby's rescue. With only a minute left, Harper flighted a long cross into the goalmouth. Wanchope lunged at the ball but made insufficient contact, which was fine for Sturridge since he thrust in the equaliser. Even so, Derby's manager Jim Smith concluded: "This Chelsea team are very serious Championship contenders indeed."Reuse content