The Saints had conceded five goals in the two opening games and Koeman opted to switch to a back three for the visit to Vicarage Road. He was reasonably pleased with how the tactical change worked out.
“It’s positive, because we received too many goals in the last two games. Five is too much in my opinion and that was the difference between the start of this season and last year,” he said.
“We did the system a little bit different, but it gave us confidence. We had good organisation compared to before. Now we had more security with the one more defender and we defended well.
“In the second half we had more domination in the game and we had some good opportunities. That’s different, but the rest of the team was the same like last year — good organisation, good teamwork. Then you need to score.”
Odion Ighalo and Etienne Capoue each had an excellent chance to snatch all three points for the Hornets but both failed to convert from close range as the teams were forced to settle for a point.
Watford manager Quique Sanchez Flores admits he thought his side had taken the lead when the ball reached Capoue two yards out, only for the Frenchman to head over.
“Yes of course (I thought it was in),” Flores said.
“Every time we got close to the goal, we tried to breathe deeply because it is very difficult to create.
“We had a very good chance in the first half with Ighalo and we had a good chance in the second half with Capoue. But it’s football.”
Southampton duo Sadio Mane and Victor Wanyama, linked with moves away to Manchester United and Tottenham respectively, both started the fixture but Mane left the field through injury just 25 minutes into the first half.
It means Watford have now drawn all three of their opening matches of the campaign while Southampton find themselves in the relegation zone after two draws and a defeat.
Meanwhile Virgil van Dijk will play for Celtic in their crunch Champions League play-off clash with Malmo tomorrow night.
Reports suggest that Southampton had won the race to sign the 24-year-old Dutch defender in a £10million deal, and that consequently he would miss the second leg in Sweden to join up with the south coast club.
However, a spokesman for the Scottish champions said: “The story is absolute nonsense and Virgil will play on Tuesday. We have no agreement with any club.”
Gomes, Nyom, Prodl, Cathcart, Holebas (Diamanti 46), Capoue, Behrami (Watson 86), Anya, Ighalo, Jurado, Deeney.
Stekelenburg, Caulker, Fonte, Yoshida, Cedric Soares, Romeu, Wanyama, Steven Davis (Ward-Prowse 72), Targett, Pelle (Rodriguez 79),Mane (Long 25).