Moses can be replaced, says Martinez
Despite selling the young attacker - one of the key personnel in the Latics successfully beating the drop last season - to Chelsea, the club still managed to record a win at St Mary's with goals from Franco Di Santo and Arouna Kone.
Martinez said other members of his squad are now ready to step up, with the extra competitive edge aiding the team.
"I think the whole team took responsibility after losing Victor Moses. He leaves with our blessing. He has done everything he could to help our football club and with that he helped his career," the Spaniard told Sky Sports.
"He arrived aged 19 and you get really attached to him, but I think this group of players are desperate to fulfil his responsibility and his boots.
"We've got three games in this busy week. You're going to see a lot of players given an opportunity to show what they can do and that is a competitive edge we have in this group."
Martinez was also delighted with his side's performance in a tough atmosphere as Southampton hosted their first Premier League game in seven years in front of a near-capacity crowd.
"I think to say that I am pleased would be an understatement. I am very, very satisfied because we knew how difficult it would be and I thought the first half-an-hour showed that," he said.
"We started to keep the ball well, we opened up a few good opportunities and then to score two goals from open play away from home is always tremendous."