The Saints played out a 2-2 draw with Leicester at St. Mary’s Stadium in the Premier League.
Koeman’s side took the lead in the 21st minute through central defender Jose Fonte, and on 37 minutes former Celtic centre-back Virgil van Dijk doubled the advantage.
Leicester came out strongly in the second half and scored twice through Jamie Vardy to earn a share of the spoils.
Following the match, Southampton boss Koeman took to Twitter to express his disappointment.
After a good 1st half, 2nd half was tough and the opponent strong! Still, we could have done better.— Ronald Koeman (@RonaldKoeman) October 17, 2015
Over the course of the 90 minutes at St. Mary’s Stadium, Southampton had 50% of the possession, took 14 shots of which six were on target, and earned six corners.
The Saints are eighth in the Premier League table at the moment with 13 points from nine matches, just four points behind fourth-place West Ham United.