In the past, Spurs gambled massive sums on players who were far from certain to be Premier League hits.
Mabbutt, 54, told the Daily Star: “Last year a lot of people were expecting us to sign a striker in January but it didn't happen.
“We needed something in that department and this was clearly seen by the management.
"Yet they didn't just rush out and buy anything. They only want players who are sure to settle into the Tottenham mould.
“Obviously, Janssen was on the radar for a while. Now it's come to fruition and he's an excellent addition."