The Kiwi took charge at Parc y Scarlets in 2014 and after winning the 2016-17 Pro12, his side are set to face Leinster in the semi-finals of the Champions Cup on Saturday.
Warren Gatland is expected to step down from his role as Wales coach after the 2019 World Cup and Pivac has held informal discussions with the Welsh Rugby Union about taking over.
The Kiwi looks a suitable candidate for the position and having previously coached internationally with Fiji, Ruddock believes he could be the right man to take the job going forward.
"He's got to be right up there. I've been very impressed in the way he's gone about his business,' said Ruddock.
"When I was Wales coach I went up against him as Fiji coach and I think a late drop-goal saved our blushes because Wayne had the Fiji team very well prepared.
"He's been around the block, he knows his stuff and he's done a great job at the Scarlets.
"He knows Welsh rugby and he knows about preparing teams for international rugby, so he's a very good candidate."