The England striker failed to replicate the goalscoring impression he made on debut in Saturday's uplifting win over Manchester City but the change in the side since his arrival last week has been marked.
Villa were rewarded for a fine attacking display as they saw off a battling Wigan side to win 2-1 at the DW Stadium with goals from Gabriel Agbonlahor and Ashley Young.
Houllier said: "Sometimes when you recruit a player it takes five or six games before he settles or scores a goal.
"Darren scored a vital goal against Manchester City and today I think he was very important in the offensive front.
"His movement is very good but when he doesn't score, it is good if the others score and today Gabby and Ashley did."
Source: PA
Source: PA