Arsene Wenger hailed Alexis Sanchez’s unique qualities after the Chilean opened the scoring in Arsenal’s 2-0 victory at Southampton and then created a second goal for substitute Olivier Giroud.

Wednesday’s victory took Arsenal to within three points of the Premier League top four and keeps alive the possibility of a 20th successive season of Champions League football for the north London club.

Sanchez broke the deadlock in the 60th minute at St Mary’s, gathering Mesut Ozil’s pass and leaving two defenders sprawling before firing home his 20th goal of the league campaign.

“The goal he scored tonight shows what he’s about: very good technique in a short space,” Wenger said. “He scores important goals. He has invention in his head. He’s creative, not phased by anything, and he surprised everyone in the stadium tonight with his goal. Everyone was expecting him to take a shot, but he’s very quick on the move.”

It was Sanchez’s cross that Aaron Ramsey headed back across goal for Giroud to nod in the visitors’ second goal in the 83rd minute.

“Giroud came on and the second goal was very important for us, too,” Wenger added. “We had to [dig deep] because Southampton started at a strong pace. The first half was quite even, but we were focused and determined. I felt if you look at individual performances you couldn’t be disappointed from the goalkeeper to Danny Welbeck. Everybody played well.”

Now Arsenal must keep the pressure on the top four by showing the same focus and winning their three remaining matches, starting at Stoke City on Saturday. Wenger knows that even nine points might not be enough to guarantee a top-four finish, but he says his team have no option but to win the games in front of them.

“I don’t know more than you,” said the Frenchman, who is still to announce whether he will remain at Arsenal beyond the end of the season. “But I believe that, for us, it’s important to maintain the focus and intensity in every single game.

“We’ll need another strong performance at Stoke. We came to a difficult ground today and we go to another on Saturday. We know we can only win our games and we had a strong performance on Sunday [beating Manchester United 2-0] and a strong performance today. So let’s just continue.”

Oxlade-Chamberlain blow

The win at St Mary’s was Arsenal’s first away to Southampton in the Premier League since December 2003. But Wenger dismissed suggestions that it showed extra character on the part of a team that has been accused of lacking that vital quality.

“I never questioned the character of my side,” he said. “It’s not because you lose games people expect you to win that you have no character. We went through a bad patch. It’s a good opportunity to show your character, how you come back and how you recover. But let’s not go too quickly to conclusions. Let’s focus and give everything at Stoke on Saturday.”

Wenger is likely to be without Alex Oxlade-Chamberlain at Stoke after he left the field in the first half with a hamstring problem. But it is too early to say whether he will be back in time for the FA Cup final against Chelsea on May 27. “He was walking properly. It was tight, not like a knife,” Wenger said. “It was more fatigue, but it’s difficult to assess so close.”

Southampton remain 10th after failing to find the net for the third game in succession. “We cannot find the good clinical edge,” said beaten manager Claude Puel. “Every time it was interesting, I think, the play. Just not enough.

“All the games the same thing. We saw our games since the beginning of the season, many games where we’ve had the same feeling. Opportunities, chances, good play, but no clinical edge.”