"It was important that we didn't go backwards" said McFadden. "[Tuivasa-Sheck] He's an extremely good player. Both Sam and Roger are probably a little bit different in terms of styles but certainly Roger would fit into our style of football.
"He's a dynamic runner and he's only still learning the position and he's going to get better so we think we've got a good one there."
Months of speculation over Tomkins' future in New Zealand was settled with confirmation today that the Warriors had granted the England international an early release from the last year of his three-year contract.
The 26-year-old will return home to the UK, with homesickness cited as a major factor.
His imminent departure enabled the club to move ahead and sign Tuivasa-Sheck to a three-year deal, believed to be in the vicinity of $800,000 per season.
"It's a negative to see Sam going back to England at the end of the year," said Warriors chief executive Jim Doyle.
"At the same time it's a positive announcement in us being able to secure Roger Tuivasa-Sheck for the next three years.
"Roger was always one that we had talked about, was always on our mind. Sam was originally here for three years.
"We talked about succession planning for after that, who would be the ideal person, and Roger was always on the top of that list. With him agreeing to come on-board that allowed us then to allow Sam to go back to England."
Tomkins said he had struggled to make the decision to leave and felt relief at having the situation resolved, while his playing future in England is yet to be determined.
"It certainly hasn't been an easy decision for me," Tomkins said. "I went to Cappy [McFadden] and Jim about a month or so ago and said I'd been feeling a little bit homesick.
"It's a brilliant club and a great place to live but I'm probably a bit more of a home bird than I thought.
"I'm not too sure where I'll be [next year]. Hopefully it will be sorted in the next few days but I've not signed anything yet."
Tomkins is currently sidelined with a knee injury suffered in the round three match against Parramatta but is focused on returning to action in the next month.
"I just want to get back on the field now and finish the year off on a massive high," he said.