Gallagher is considered one of the many talented young players to have emerged from Southampton's youth academy in recent times but the striker has not been able to make a mark in the first team as his campaign last year was ravaged by a serious knee injury.
The 19-year old has now made a full recovery and has stated that he is looking to impress manager Koeman during the upcoming Premier League campaign.
Gallagher told the Daily Echo: "It's definitely a fresh start for me and a new season where I can hopefully be injury free and maybe impress and maybe have an opportunity in one of the Europa League games or all the other fixtures that we've got coming up."
Gallagher added: "I sort of feel like I have had an opportunity and I've done alright when I've had it, so it's not so much like I'm going into unknown territory when I come on, so I'm looking forward to getting back in and maybe getting a chance in the Premier League again.
"Hopefully it will mean he has to use more players and give more opportunities to maybe the younger boys as well, or maybe just bring a few more players in.
"I think it just shows how important pre-season is to maybe put my mark down."