It is almost a fortnight since the 48-year-old stepped into the void left by Chris Wilder.
While little has changed in the way United have prepared for the three games since then, behind the scenes players have enjoyed a change in the mood.
Lewis is a different character to Wilder, which has influenced the atmosphere, but the stand-in boss will not hesitate to show another side if standards slip.
“I think most people have a little nasty streak in them,” he said.
“We’re not doing much differently in my opinion from what we have been doing.
“I think the players know I am a relaxed character, but once you walk over the line in training I expect the sessions to be full-on and really ‘at it’.
“The lads are like that and the only time I think I’d probably get a little bit annoyed would be if the training wasn’t at the tempo we want.
“Up to now it has been all season and I don’t see any reason for that to change.”
Lewis has not had to lay down the law yet, although more established players have been on the receiving end in the past.
He said: “I think some of the lads who have been here a bit longer have seen it the odd time.
“One thing I won’t tolerate is a lack of effort in training and we’ve never had that this year.”
Since taking charge, Lewis has guided United to hard-fought away draws at Exeter City and Bury, either side of a home win over AFC Wimbledon.
It has taken the side back into the top three ahead of tomorrow’s trip to Bristol Rovers.
With chairman Ian Lenagan making it clear the search for Wilder’s replacement will not be rushed, the caretaker has an extended chance to stamp his authority on the side.
When asked if he was becoming more comfortable in charge as time went by, Lewis praised the role of staff and senior players.
“I’m surrounded by really good guys on the staff. We’re really level-headed and we all get on well, which is a good thing,” he said.
“We can always take the tension out of it because we have a good time together during the day.
“We have some really good experienced players as well and we have to trust them.
“They get good information from everybody and they use it well.
“When you’ve played 300 games, as some of them have, I’m not saying we just let them get on with it, but you do have to trust them.”