A Victor Ruiz own goal put Barca in front in the 68th minute before the same man restored parity seven minutes late, but another substitute, Francisco Trincao, grabbed a crucial winner for Koeman's side three minutes from time.

Koeman told Barca TV: "It's great, another three points in a difficult match and I think we started a little bit slowly – maybe about the number of games we've played.

"It was not the team that I like to see, but OK that's normal after many games away from home, but during the game we came better and scored good goals and had a good reaction."

The victory made it six in a row for Barca in LaLiga and they are back to second after briefly dropping to fourth following wins for Real Madrid and Sevilla this weekend.

After a tricky start, Koeman has now masterminded a run of one defeat in 16 for the club he represented with distinction during his playing career.

While Messi's arrival sparked the turnaround, midfielder Frenkie De Jong also impressed at centre-back after he was introduced in the 11th minute for the injured Ronald Araujo.

De Jong completed all 82 of his passes and another substitute who made his mark was summer signing Trincao, who produced a wonderful finish to open his account for his new club after a difficult spell following a July switch from Braga.

"I'm really happy. Happy for the win and we have to keep it like that to win the next game," the forward told the official club website.

Next up for Barca is a return to Andalusia on Wednesday to take on Sevilla in the Copa Del Rey.

Betis boss Manuel Pellegrini was left to reflect on Messi's genius.

He told reporters: "Football, no matter how much intensity and tactics are talked about, the difference is made by technique, the individualities are decisive.

"And Messi is the best in the world. He makes a difference every time he enters. He does not forgive and put Barcelona in the game."