Wenger was less than pleased, he continued: "We're not happy because we wanted to win but when you can not win at least don't lose".
'We deserved to get a point for the second half performance, ' he said. It was a clinical from Saints but another woeful early defensive error from Arsenal.
But the Gunners will feel it was two points dropped in their pursuit of a top-four spot.
"It was a bit in their head and they were a bit apprehensive to start well again and that's why it is sometimes not good to talk about the problem because you create a bigger one".
A poor clearance from Mertesacker ceded possession deep inside his own half and he then slipped as he attempted to make up for his mistake, allowing Dusan Tadic the time and space to pick out Austin's run into the box where the striker finished from 12 metres out.
This comes after Giroud came off the bench to rescue a point for Arsenal against Southampton on Sunday.
Arsene Wenger makes a promise to Oliver Giroud as he admits he is 'not happy' after Southampton draw
For Southampton, Maya Yoshida and Jack Stephens are among the changes, while Charlie Austin starts another game up front.
The veteran manager wasn't happy at all after Arsenal's disappointing 1-1 draw with Southampton at St Mary's this afternoon.
Wenger also revealed his ire at the perceived time-wasting tactics of the Saints.
"The second half was played in one half of the pitch and it was important not to be caught on counter attack". It's very frustrating to give the advantage to the guy who made the foul.
Despite seeing most of the ball, Southampton had the two best chances of the game.
Richard Keys urges West Ham United fans to support David Moyes
However, Moyes hinted Hart could find himself back into the starting XI, given West Ham are still competing on three fronts. And Hart's inactivity under Hammer boss Moyes leaves the 30-year-old's place in serious jeopardy.