The Saints came from being behind at half-time to edge out the Devon outfit 24-21 to secure a bonus-point victory and make it two wins from two games at the start of the new Aviva Premiership season.
While he was happy to get the win, Malliner admits that his side weren't entirely in control of the game.
"Our performance was a mixed bag," said Mallinder.
"We were good in the first 20 minutes, scoring two good tries, but then we relaxed, kicked loosely and going down to 14 men put us under some considerable pressure.
"However, we kept our cool in the first 10 minutes of the second half and then our forwards went on to dominate."
Next up for the Saints is a trip to Bath on Friday.