Dellien broke his opponent four times in a two-hour, one-minute triumph on Court Simonne Mathieu, capitalising on the former World No. 3's below-par effort.
The Barcelona Open is one of the more important tournaments before the Roland Garros, therefore players will be eager to improve their game in a competitive setting on clay.
The final set of the match went to a tie-break with the Bulgarian recording a 6-4, 3-6, 7-6 (7-2) win over the Pole.
Aside from winning five singles titles, he has also finished runners-up in nine other finals, the most notable of those being the 2017 ATP World Tour Finals.
Dimitrov has won 8 singles career titles, with all of them being ATP singles titles and is by far the most successful tennis player from Bulgaria.
With hard court as his favourite and double-handed backhand as a favourite shot, Krajinović is often compared to Andre Agassi
Rublev continued his stellar form in Indian Wells, reaching the semi-finals for the first time after winning back-to-back ATP Tour titles.
ATP has him ranked as high as world No. 22 in singles, which he achieved on September 27, 2021, and he is currently the British No. 2 in singles.
Rublev has been near the top of the mountain of men's tennis for quite a while now and has played against some of the best.
Dimitrov was called 'Baby Federer' at one point in time, due to the similarities in gameplay between the two players.