Wenger's team won just one of their four league games last month -- a run that means they will head into the latest round of fixtures in third place, three points adrift of leaders Leicester City.
The weekend's FA Cup fourth-round victory over Burnley helped draw a line under the disappointing home league defeat by Chelsea six days previously, which raised questions about the Gunners' consistency.
Sanchez and Coquelin both made their first starts in two months against Burnley at the Emirates Stadium on Saturday and their returns could hardly be better timed.
Wenger believes Sanchez will benefit from the enforced lay-off and the forward looked sharp against Burnley, making one goal and scoring another in a 2-1 win that kept Arsenal on course for a third successive FA Cup triumph.
Coquelin's work in front of the back four has also been missed and with the fixture schedule about to become even more demanding when the Champions League resumes this month, the Frenchman's availability will ease the load on his fellow midfielders.
Wenger must decide how many changes to make to his line-up after making nine alterations against Burnley.
Calum Chambers came in at right-back and scored, but is expected to make way for Hector Bellerin, while Per Mertesacker should return to the heart of the defence in place of Gabriel after serving a one-match ban.
- Targett 'wary' -
Mertesacker was dismissed against Chelsea for bringing down Diego Costa, but Wenger has no doubts about the continuing importance of the Germany international to his team.
"We forget the amount of times Mertesacker saves a goal from going in and that happens," the Arsenal manager said.
"The risk is part of the game and you have to feel comfortable with that. Mistakes are part of that competition, but we learn from defeat."
The victory over Burnley came at the cost of a fresh injury to Tomas Rosicky, who suffered a thigh injury after making his first appearance of the season as a second-half substitute and faces another month out.
Southampton head to north London on the back of three successive wins, including a 1-0 victory at Manchester United last time out.
That run has revived the club's hopes of forcing their way back into contention for a Europa League place. They begin the week in eighth place, four points off the European qualifying positions.
Left-back Matt Targett said: "The form we're in at the moment, I think we can beat anyone in the division, so it's important that we go there with confidence, but we need to be wary as Arsenal are such a good team.
"It would be a massive result if we could go there and get a win or a draw. I think it would give us confidence going forward and we can take it from there.
"I think it's West Ham after that, so we can go into that game with our heads held high and just play our football."