The fullback, who has just eight Premier League appearances to his name this campaign, has joined Brazilian outfit Gremio on loan for the remainder of the season following the January acquisition of Malaga left back Nacho Monreal.
And Wenger feels Santos, who he insists he still values highly, will be better served in his homeland.
"He moved because he'd lost a bit of confidence and he needs to play," Wenger told reporters. "He's a guy who's a very good football player, but he didn't get enough games.
Wenger believes the left-sided defender is suited to an more attacking role, but acknowledges the stiff competition for places at Arsenal with the likes of Theo Walcott, Lukas Podolski, Andrey Arshavin & Co. ahead of the 30-year-old in the pecking order.
“He's more at ease in my opinion on the left of midfield, where there's a lot of competition.
"He will be back at the end of July, and of course he can have a future at Arsenal. That depends as well on the ins and outs during the summer."