Both sides are still searching for their first Premier League win of the season, while Shane Long could be given his first start since moving to St. Mary's.
Southampton was defeated 2-1 at Anfield on Sunday in the Dutchman’s first Premier League game at the helm.
Koeman’s men were unlucky not to gain a point from the match after enjoying the better of the second half but Daniel Sturridge popped up with a winner 11 minutes from time.
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An exodus of key players and the departure of coach Mauricio Pochettino to Tottenham raised concerns that Koeman's side could struggle this season, but the display at Anfield suggested otherwise.
Koeman was encouraged by the manner in which his new-look side took the game to Liverpool, but knows the club faces a different challenge against West Brom as it will be expected to start with a win in front of their supporters.
"We played on a good level [against Liverpool], we played an amazing second half," he said. "The result was not what we deserved, but I think it was good for the confidence, because I believe everybody was a little bit afraid of how Southampton was going to start the season against a good team as Liverpool is. But we showed our qualities and showed we are a team who can be very competitive to everybody.
"We know for this Saturday it will be different, maybe more difficult because everybody expects the same level and we play at home. We have to play on the same level we did against Liverpool, but I think the belief is in the team, the belief is in the players and we look forward for Saturday."
Center back Florin Gardos must wait to make his Southampton debut because of a hamstring injury and striker Jay Rodriguez (knee) is a long-term absentee.
Koeman must decide whether to hand a first start to Shane Long, who is poised to make his home debut against one of his former clubs.
Goals from Rickie Lambert and Adam Lallana ensured Southampton beat West Brom 1-0 on both occasions last season, but both players are no longer at the club after moving to Liverpool.
The visitors are also embarking on a new era under coach Alan Irvine and they looked set to making a winning start under the Scotsman until Sebastian Larsson struck five minutes from time to salvage a 2-2 draw for Sunderland on Saturday.
Saido Berahino scored twice in Irvine's first Premier League game in charge at The Hawthorns and the young striker is set to lead the line once again.
Irvine said that his entire squad trained Thursday, so Joleon Lescott and James Morrison could return after missing out against Sunderland because of knee injuries.
The former Everton assistant manager stated that Cristian Gamboa will not be in contention to make his debut as he continues to build up his fitness.