It is simply that they seemed to need every ounce of resolve, every last drop of sweat in their bodies to struggle through last season. Logic says it cannot go on forever. At some point, surely, they will run out of fuel.
Naturally, Martin O'Neill does not care to dwell on such a possibility, although he is an intelligent, thoughtful man and as such is bound to have wondered just how much pushing his players can take.
As last year, his first season with Leicester in the Premiership, O'Neill's target is simply not to be relegated. "Three down, 39 to go," he quipped on Saturday, his mind already on the 42 points he reckons will ensure another happy ending.
"Much as I'd like us to retain the Coca-Cola Cup and win the Uefa Cup," he says, "our first and most important task is to get over the finishing line in the Premiership."
For a club of Leicester's resources, unwilling to pay inflated fees and bank-breaking wages, O'Neill reckons the only way to hold on to a place alongside the wealthy elite is to plan carefully and work tirelessly. Thus on Saturday, guessing correctly that Villa would field Stan Collymore, Dwight Yorke and Savo Milosevic in a boldly attacking formation, O'Neill deployed Pontus Kamark to shadow Yorke and trusted his three central defenders to snuff out the other two.
It worked out perfectly. For half an hour, Villa battered at Leicester's door but failed to force it open. Then, as their opponents paused for a breath in the stamina-sapping heat, Leicester took the opportunity to make their own mark, Steve Guppy delivering a splendid deep cross for Ian Marshall to climb above Alan Wright (not a difficult task) and head home.
Thereafter, Villa's effectiveness declined while Matt Elliott and Spencer Prior, powerful figures at the heart of Leicester's defence, appeared more and more to have the measure of Collymore and Milosevic.
It left Brian Little, whose side are seen as dark horses for the title, feeling somewhat bemused, having seen Villa fade as they so often did last season, despite the presence of the pounds 7m Collymore.
Questions will be asked about the formation, not least because the inclusion of a third striker at the expense of a fifth defender undermined what, last season, was Villa's great strength. It is something for Little to ponder over before taking on Blackburn at home on Wednesday.
Leicester are at Liverpool on the same evening, the start of a daunting sequence that includes games against Manchester United, Arsenal and Sheffield Wednesday before the end of the month.
Goal: Marshall (37) 1-0.
Leicester City (5-3-2): Keller; Kamark, Prior, Elliott, Walsh, Guppy; Izzet, Lennon, Campbell (Savage, 83); Marshall (Claridge, 88), Heskey. Substitutes not used: Fenton, Parker, Andrews (gk).
Aston Villa (4-3-3): Oakes; Nelson, Ehiogu, Southgate, Wright; Taylor, Draper, Townsend; Milosevic, Collymore, Yorke. Substitutes not used: Joachim, Grayson, Scimeca, Charles, Crichton (gk).
Referee: S Lodge (Barnsley).
Booking: Villa Taylor.
Man of the match: Elliott.
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