Dimitri Payet believes West Ham's last-gasp victory over Accrington Stanley in the EFL Cup in midweek will boost their confidence to improve their form in the Premier League.
"I am working hard on all aspects of my game," Payet toldwhufc.com. "On Saturday, I hit the post with the free-kick and yesterday, it went in.
"The goal helped us a lot and makes us feel a lot better because it meant we avoided extra-time and another 30 minutes of football.
"It will be great for our confidence."
"Sunday's game against Southampton is, of course, one that we can win and we will be doing all that we can to do so and to take the victory at home," he added.
"We know that we are in need of points, but we are at home and I think that the last-minute victory against Accrington will have helped us mentally and will have boosted our confidence and I hope that we will see that on the pitch on Sunday."