South African No.8 Van Velze had a difficult start to life at Northampton after joining the club from Super Rugby side Blue Bulls.
The 24-year-old picked up three yellow cards in his first eight appearances for the Saints, also picking up a four-week ban for a tip tackle on Exeter Chiefs’ Will Chudley.
But he has come back with a bang since the suspension and scored two crucial tries in recent weeks to help his side seal vital wins at Ulster and Exeter.
And director of rugby Mallinder expressed his happiness at seeing the youngster find his feet in the English game.
“I think we as coaches are delighted with van Velze,” said Mallinder.
“I guess not many people knew about him but we’d been watching him for a couple of years playing back in South Africa.
“It does take players when they come from other countries, time to adjust to the Premiership. Playing in the Premiership is different and it’s probably taken him a bit of time to get used to it, but he’s enjoying it now and we’re seeing the results in his performances.
“In not brilliant conditions over the past couple of weeks, he’s been very strong and he’s playing very well.”