He finished in the top 10 in his first event, the 2012 Africa Open. He finished the season in the top 100 of the Order of Merit. In February 2014, Grillo had his best finish to date on the European Tour, when he finished runner-up behind Stephen Gallacher at the Omega Dubai Desert Classic.
Later in the season he finished 8th at the Bayerische Motoren Werke International Open and the Bayerische Motoren Werke Masters, and 11th at the Turkish Airlines Open.
Grillo turned professional in 2011 and earned playing status on the European Tour via Qualifying School. He ended 44th on the European Tour Race to Dubai. Grillo began the 2015 European Tour season with a third place at the Volvo China Open, a fifth place at the Qatar Masters, a sixth place at the Open de España and an 11th place at the Shenzhen International.
He lost in a five-man playoff at the Puerto Rico Open on the Professional Golf Association Tour, playing on a sponsor"s exemption, and finished tenth at the Barbasol Championship.
In just seven starts, he earned enough to qualify for the 2015 Web.com Tour Finals. He claimed a ninth place at the Hotel Fitness Championship, a runner-up at the Small Business Connection Championship and a first place at the Web.com Tour Championship.
Therefore he finished second at the Finals money list and got a card for the 2016 Professional Golf Association Tour. Since Grillo only played in seven events during the 2014-2015 season, he was still considered a rookie for the 2015-2016 season.
He made a 25-foot birdie putt on the 72nd hole for 3-under-par 69, which was later tied by Na.
The victory gained Grillo entry to the Masters and the 2016 Professional Golf Association Championship. He also moved up to 36th in the Official World Golf Ranking. 2011 Terra Cotta Invitational Professional Golf Association Tour wins (1) Web.com Tour wins (1) Professional Golf Association Tour Latinoamérica wins (1) Amateur Eisenhower Trophy (representing Argentina): 2008, 2010 Professional World Cup (representing Argentina): 2013.
