The Ireland international helped the West Yorkshire side to their biggest ever win at Hull FC on Good Friday, an emphatic 52-24 success that leaves them just two points behind leaders Castleford Tigers.
In contrast, Widnes – where Mullally started his career – have won just once in nine games so far having lost again against Warrington Wolves last Thursday.
“When we played Warrington they hadn’t won a game and look what they did,” insisted the front-row, Leeds losing 25-14 at the Halliwell Jones Stadium 10 days ago.
“You can’t under-estimate anyone; Widnes are a good team regardless of where they are in the league.
“It’s my hometown team and I always look forward to playing them.
“If we can get another win we will be in good shape, but we’re happy to stay under the radar and hopefully at the end of the year we’ll be up in the top-four.”
Leeds have named an unchanged 19-man squad although Liam Sutcliffe (head) and Ashton Golding (thigh) will need to undergo fitness tests ahead of kick-off with Mikolaj Oledzki and Jordan Lilley waiting in the wings if needed.
On the victory at Challenge Cup holders Hull, 25-year-old Mullally added: “It was a good performance, especially in the first half.
“We didn’t want to take our foot off the gas in the second; they got back into it a bit, but we took control back and finished them off.
“After the loss at Warrington we needed a big response and we did that.”
Leeds had not scored a half century of points against Super League opposition since the 50-0 Ladbrokes Challenge Cup final demolition of Hull KR in August 2015.
Former Huddersfield Giants player Mullally feels such improved attack has been built on strong defence.
“I think defensively is where the ruthlessness is,” he said.
“We are really enjoying defending with each other. If someone misses a tackle someone else is going to clean up.
“We know we’ve got a commitment and trust in each other. In attack we’re definitely getting there, getting better each week.”
Mullally, who signed at the end of 2015, made only his second start for the club at Hull and scored a fine solo try at the death, his third of the season.
Brad Singleton completes his six-game ban today, though, and Keith Galloway returned after a seven-month injury at FC so competition is set to increase.
“I am just happy to be in the team each week and trying to build some consistency,” he said.
“I’m not getting carried away with anything, but am enjoying it. You have to concentrate on playing well each week, being consistent and hopefully staying in the team, because you are never safe.”
Patrick Ah Van is one of six players added to the Vikings’ squad, but captain Joe Mellor misses out.