Long, who feels he’s in the best run of form during his time with Southampton, has started every game since the 4-0 success against Arsenal on Boxing Day.
In that time the striker, who celebrated his 29th birthday on Friday, has netted three goals and helped Saints move up to tenth in the Barclays Premier League.
Austin’s arrival, and Graziano Pellè’s return to fitness, mean Ronald Koeman has plenty of options going forward, but Long is determined to keep hold of the shirt.
“I think it might be my shirt to lose at the moment, so it’s a strong position for me to be in,” Long told youtube.com/southamptonfc
“I’ve always said that competition pushes every player. It pushes every player to play to their best because there’s someone waiting there to jump in and take your spot.
“I’ve waited a long time to get this lead role in the team and I’m not going to let it go easily.”
Long believes Austin, who could make his debut for Southampton at Old Trafford, provides Koeman with another option going forward, and the Irishman feels he could work well with the former QPR man.
“I think everyone can see last year in the Premier League he scored 18 goals, so he’s very clinical when he gets his chances,” Long added.
“He’s someone I feel I could work with alongside upfront and it’s a different option for the manager. We’re different players and he’s a very good player.
“When the gaffer wants to give Charlie a run in the team, I’ll be supportive. I’m looking forward to hopefully getting the chance to play with him and create a good partnership.”