Villa were unable to stop United clinching the title with a 3-0 win last Monday, a result that left Lambert's side only three points above the relegation zone having played a game more than 18th-placed Wigan. But it was only a second defeat in their last six matches and a haul of 10 points during that run has generated some much-needed optimism.
An extra incentive for Villa is the knowledge that victory on Monday will draw the club level with Sunderland, who have pulled themselves away from the bottom three. Lambert said: "We have to win. The next four games are massive games but we also know if we win on Monday then you pull Sunderland right back in as well."
The Scot went on: "There's only three points in it. We're at home. We'd rather be at home than going away, that's for sure. You'll have the crowd behind you, you'll have everything behind you.
"The thing for myself is we're playing well enough, we're creating chances. It would be different if I was going into that game and we weren't playing well or creating, then it becomes a big thing."
All Villa's remaining games are likely to be huge for both teams, with Norwich, who are not yet out of danger, and Champions League-chasing Chelsea to come before a potentially decisive final-day clash with Wigan at the DW Stadium.
Last Monday was arguably a less than ideal time to visit Old Trafford but Lambert had no complaints, his only regret being their failure to prevent United scoring three times inside 33 minutes.
The Scot said: "I don't think it mattered when we went there or what happened between Tottenham and Manchester City. It was always going to be tough, regardless of what the occasion was going to be.
"I think the only difference was the crowd came with that vibrancy knowing that if they could beat us then (they would win the title), that gave them a lift, but it was always going to be tough going there. We were up against the champions elect. One thing going to Old Trafford is you have to try to stay in the game as long as you can and try and create chances.
"We created chances to score, it never materialised, but sometimes you have to hold your hand up - the second goal was fabulous, you could have had three goalkeepers in there and they wouldn't have saved that."