And Rees, who made his first appearance since October after undergoing medical treatment at Velindre Hospital, spoke after the game about his emotional return.
"It has been a tough couple of months for me, but I am a positive person," he said.
"I was fortunate that I could train throughout the treatment. But the support I have had from then rugby world has been great and overwhelming.
"It was a great performance tonight and hopefully we can carry this forward. I've been out for a long time and it was a fast game. But I will take the 20 minutes I had and hopefully I can build on that."
"It was a very physical game and we knew what Ulster would bring," he added.
"It's been a disappointing season for us and it was disappointing against Ospreys last week, we have had some harsh words this week. We did a great job to turn around.
"We played with the right attitude and physicality, for the whole 80 minutes.
"Credit must go to Johnsy (Paul John) and Chief (Dale McIntosh) who have worked hard with us and the boys have gone out and played. We deserved the result.
"We took the game to them in the first 20 minutes. We gave away a soft try, but other than that we looked comfortable in defence.
"It was the last game of the season here and it was important to get that result. We can now look forward to Edinburgh."