Villa's place in the top flight is under threat this season as they struggle to score goals, and as a result find it difficult to win games - they have only won five so far.
Lambert was dismissed on Wednesday after Villa slipped into the bottom three following a 2-0 defeat to Hull City.
Banners and chants during Tuesday's defeat called for Lambert to leave the club - they got their wish 24 hours later.
Following his departure Lambert released a statement saying leading Villa was the "toughest challenge" of his career, and Marshall agrees, saying a novice would struggle under the pressure.
"This is not a job for someone to cut their teeth on," said Marshall. "This is all new to me, but I'm happy to do it while things are being sorted.
"It's a big job."
The likes of Tim Sherwood and Sean Dyche have been linked with the vacancy at Villa Park, although no move has been made to replace Lambert heading into this weekend's FA Cup clash with Leicester City.
Marshall prepared the team to face Leicester on Sunday, and has seen a determination from the players to turn their fortunes around.
"I don't think the players have a point to prove," he added. "They want to go out and win the game because they are good professionals and there is a quarter-final place at stake."
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