The former midfielder – who played 199 times for Doncaster over two spells – makes his first return to the Keepmoat Stadium as a manager today when Oldham Athletic visit.
Wellens took over at the League One club from John Sheridan in September and has lost just three times in his 16 games so far.
Strachan said: “It doesn’t surprise me what he’s doing. When he was leaving here he was talking about an interest in coaching.
“I worked with him a bit when I was on trial at Blackpool and for a short time at Doncaster and you could see what an intelligent footballer he is. It speaks for itself, the run of results they’ve been on and where they were when he took over to where they are now.
“His team is a good reflection on what he was as a player; it’s pleasing on the eye, centred around good passing and moving football, very exciting, very entertaining and very fluid.
“They’re a really good footballing team in good form beating Northampton 5-1 last week so we’ll have to be at our best.”
Oldham won just one of their opening 11 games this term under Sheridan but Wellens – in his first managerial appointment – was unbeaten in his first seven games, winning five.
They are now up to 16th place, three points in front of their hosts.
Wellens, 37, joined Oldham on loan shortly after current Doncaster manager Darren Ferguson arrived in October 2015 and soon switched to Shrewsbury Town on a permanent deal but Strachan maintained there was no fall-out.
“I think he left on really amicable terms with the club and manager,” he said, as Doncaster seek to bounce back from a last-minute 1-0 loss at Oxford.
“It was just one where he wanted to be closer to home (Manchester) and the opportunity came up.
“His departure was really well managed with good feeling on both sides. I’m sure he’ll get a good welcome.”