The 29-year-old forward started only his fourth game of the season in the 2-1 Champions League win over Sporting Lisbon.
"Louis' last full game before the match at Bolton was last December," Fergie told manutd.com. "So you have to take that into consideration before talking about touch and confidence.
"He needs games, but it's difficult with the situation he is in with injuries. We have to be careful, but he felt great against Sporting and that's encouraging."