Saints make the trip to Hartlepool’s Victoria Park stadium on Monday afternoon for an important clash with Boro in the Barclays Under-21 Premier League.
After making 11 starts this season, Sims has been a substitute in the last three games, but he had a notable impact after coming off the bench in last week’s 2-1 defeat at Leicester City, setting up Jake Hesketh’s goal.
"I think I had a lot to prove, so I was happy with my performance when I came on,” Sims told Southampton’s official YouTube channel
. “Hopefully I can replicate that in the game against Middlesbrough.
"I need to start performing well in the games that I'm playing and hopefully I can get that place back and cement it.”
Saints are two places and four points above bottom side Boro in the table, but their opponents have two games in hand, so Sims stressed it is important they get a positive result.
“We know we have to start winning now, because if we don't start winning there's that chance of going down, so we all know there's that pressure and we hope we can get that win coming up,” he said.
"The performances have been good, but we need to be more consistent.”