Villa went down 2-0 at fellow Premier League strugglers Hull City on Tuesday, extending their winless league run to 10 matches, which dates back to a 2-1 success over Leicester in early December.
It was confirmed 24 hours later that Lambert and Villa had parted company, with Scott Marshall placed in caretaker charge.
Mired in the Premier League's relegation zone, Villa have enjoyed a little respite in the FA Cup, with wins over Blackpool and Bournemouth providing something of a boost for the beleaguered club.
Tasked with taking over first-team duties, Marshall insists it is business as usual for him and the players.
"The immediate thing for me was to take training this morning," he said in Friday's press conference.
"We have come in this morning and not changed anything in particular, we got the lads out and preparing for the game on Sunday, as we have been doing. The job was to get on the field and get on with things."
Leicester, meanwhile, have endured something of a tumultuous week themselves.
Manager Nigel Pearson became involved in a touchline altercation with Crystal Palace's James McArthur during the 1-0 league defeat last weekend, and widespread reports emerged on Sunday that he had been sacked.
Leicester soon published a statement denying such rumours, but their position at the bottom of the Premier League table was not improved by a 2-1 defeat at Arsenal in midweek.
Like Villa, the cup has proved a welcome distraction for Leicester who have disposed of Newcastle United and Tottenham in the previous two rounds, and Pearson says they can ill-afford to let Lambert's departure affect their preparation.
"We've got to concentrate on our performance," he said. "Tuesday [against Arsenal] was another example of that. It was a positive performance but we didn't get what we were looking for.
"We have to look to the next game, it's important for the players that they approach it in a very positive manner.
"We have to block out all the stuff that's happening in regard to our opponents. You have to keep your own focus on what's required and that's what I'll be doing because it's important for us to get a positive result this weekend."
Leicester are without the cup-tied Robert Huth, but Villa have been boosted by the news that captain Ron Vlaar has been passed fit after a knee injury.
