Ten Hag and Ronaldo, 40, had a reportedly rocky relationship during their time together at Old Trafford that resulted in the Portuguese forward being shipped off to Al-Nassr.
Ronaldo has continued to score goals in Saudi Arabia, recently bagging a hat-trick in their 4-0 friendly win over Rio Ave.
Speaking after their 2-0 friendly defeat to Chelsea, now Bayer Leverkusen manager Ten Hag surprisingly defended his ex-player.
When asked if Ronaldo was "still the problem" after scoring a hat-trick, Ten Hag replied: "For me, it is no problem, he was never the problem. I think that's the past, it is what happened, and after that we won two trophies at Manchester United, and I wish him all the best for the future."