Messi inspired Barcelona to a 4-1 win at the Benito Villamarin Stadium, earning an ovation from the Betis fans in the process.
Per Sky Sports on Monday, Xavi said of Messi:
"Every day he is a better player. He is unbelievable. In my opinion he is the best player in history, not just in this moment, in history.
"What he is doing is incredible. Every game he makes the difference, every game, since 12 years ago. I was playing with him and his skill, he's incredible. The best player in the history in my opinion for sure."
Xavi may be a former team-mate of the Argentinian, but there are plenty who share his view, including The Independent's Miguel Delaney and football commentator Ray Hudson:
Messi's hat-trick on Sunday was the 51st of his incredible career, and it will rank among his best.
After adding another free-kick to his ever-growing collection, the 31-year-old raced onto a delightful backheel from Luis Suarez and flicked the ball past Betis goalkeeper Pau Lopez.
Lopez was helpless went it came to Messi's third, which the No. 10 audaciously chipped over him from just inside the area with a first-time finish.
Only Xavi sits ahead of Messi in Barcelona's all-time appearance standings, but the latter broke one of the Spaniard's records on Sunday:
Following his hat-trick, La Liga shared some of the many sensational highlights Messi has produced in the Spanish top flight over the years:
While he may be behind Cristiano Ronaldo when it comes to UEFA Champions League wins and goals—Ronaldo has five titles to Messi's four and 124 goals to 108—the latter has been similarly outstanding in Europe's premier competition over the years:
Messi delivers a phenomenal number of goals season after season, and his output has continued unabated despite evolving his game in recent years to become more of a playmaker for Barcelona. He can pick a pass and dribble past defenders with the best of them, and his intelligence on and off the ball is virtually unrivaled.
Messi is a jack of all trades, and he's mastered almost all of them.