Having successfully defended his Zagreb crown, Cilic beat Jo-Wilfried Tsonga and Andy Murray on his way to the Rotterdam final, where Tomas Berdych ended his run of nine successive wins.
Cilic has always been a major talent and was one of the last players to make a real impression as a teenager, breaking into the top 30 as a 19-year-old in 2008.
But since then he has remained a step behind the leading men, with doubts over both his physical and mental strength.
Last year came the nadir when he failed a drugs test in May and was initially suspended for nine months.
To make matters worse, news leaked before the ban was announced, while Cilic also came under fire for saying he had pulled out of Wimbledon due to injury rather than because, as was really the case, he was taking a provisional suspension.
The Croatian felt he had been the victim of a miscarriage of justice, with the failed test stemming from glucose tablets his mother had bought for him.
Cilic's ban was reduced to four months on appeal to the Court of Arbitration for Sport, and he returned to action in October.
The sense of being wronged may well have given him extra impetus, but improvements in his game made under new coach Goran Ivanisevic seem to be the key reason behind his great form.
Another upheaval for the 25-year-old last year was his split from long-term coach Bob Brett, and he linked up with childhood mentor Ivanisevic during the off-season.
Cilic has certainly added bulk, and the extra power on his serve was a key factor in his 6-3 6-4 win over Murray - a player he had beaten just once in 10 previous meetings.
Ivanisevic was not with Cilic in Holland because he was competing in the ATP Champions Tour event in Delray Beach, but he followed his charge's progress with great satisfaction.
The former Wimbledon champion said: "This is so great for Marin to beat two top-10 guys in the same week, especially Andy because he is always struggling against him. It's great. I'm really happy for him.
"He is ready. He's really confident. To beat Murray in two sets you have to be playing well."
Cilic is still down at 29 in the world rankings, a legacy of his absence last year, but his success is another sign that men's tennis this season may have a different look.
Stanislas Wawrinka has shown what is possible in the grand slams, and the challenge has been laid down to the big four heading into the first Masters series tournaments of the season in Indian Wells and Miami next month.