Start slowly against Manchester United and it will be "game over in 20 minutes" for Southampton, Matt Targett has warned.
The Saints defender has challenged the south coast club to sharpen up to stand any chance of a result in Friday night's Premier League trip to Old Trafford.
Southampton started life under new manager Claude Puel with a 1-1 home draw with Watford last weekend, leaving Targett and his teammates already ruing missed opportunities.
"The first half [against Watford] wasn't good enough, and the manager said that at half-time," Targett told Southampton's official club website.
"We know we can't start the game like that against Manchester United, because it will be game over in 20 minutes.
"So hopefully we get off to a good start and we just have to frustrate them.
"It would be massive if we get something there. It will give us confidence going into the next game and hopefully we can get a good result."
Saints have pulled off 1-0 wins in both of their last two trips to Old Trafford, but will travel to a United squad transformed this week.
New boss Jose Mourinho has already stamped his influence on the club, with world-record £89 million signing Paul Pogba ready to make his debut against the Saints.
Zlatan Ibrahimovic claimed a goal on his Premier League debut as United eased past Bournemouth 3-1 at Dean Court last weekend, with Targett freely admitting Southampton are wary of the Red Devils' attacking threats.
"It will be a very difficult game," said Targett. "It's their first game at home and they're going to be well up for it, so we'll have to match it.
"I think they're going to be more attacking, I think the signings they have made will make a big difference."