Play was suspended the previous day with the pair locked in a compelling first set tie-break. del Potro emerged from the delay the next day to take the tie-break 7-5, but it was far from plain sailing for former US Open champion from there on out.
His level dropped dramatically in set two but he steadied himself in sets three and four, committing fewer errors and displaying an impressive level of fitness that has not always been synonymous with post-injury del Potro.
“It’s tough to speak now,” he sobbed courtside after the win, which will provisionally lift him up to number four in the world. “It has been a long time without a good feeling in my body.”
“I have had three surgeries on my left wrist and I was close to quitting, I don’t really have any words.
“It was very important to have the support of my family and friends and the love of you guys, you make me so happy.”
The first set could be best described as cagey, with neither player putting significant holes in their opponents serve, and it took until the ninth game of the match to bring up the first deuce game.
Cilic held comfortably then and the slower conditions, with the rain falling intermittently, certainly played a role and the opening set tie-break arrived at the most inopportune time.
The rain was beginning to fall and with both players having traded two mini-break apiece in the tie-break the players were instructed off court and play was suspended for the day.
With the sun shining and conditions on the quicker side the following day, del Potro started the more sprightly, winning the first two points to take the first set in 75 minutes.
Cilic kept his composure and a window of opportunity opened in the second set when del Potro was broken while serving at 4-4. The Argentine double-faulted on break point and he appeared to have been distracted by a member of the crowd, casting a resentful stare in the direction of the fan who was perched in the front row and ambling over to have a few choice words.
However, the Croatian, who was pushed the distance by Fabio Fognini in the fourth round, was broken to love as he served for the set, but he did not allow the disappointment to consume him, breaking the Argentine for the second time in quick succession and closing out the second set at the second time of asking.
The match appeared to be swinging in the direction of the Australian Open finalist when he grabbed the break to open set three and consolidated by winning his next two service games.
That, however, was when the tide turned as del Potro broke back to 40 before breaking for a 5-3 buffer. From successive service holds to being broke twice in successive service games, Cilic was now watching the Argentine serve for a 2-1 lead.
And he duly he did so, while also ensuring he did not take his eye off the ball like he did at the beginning of the previous set.
The duo traded blows in the fourth set but neither were willing to part with break points. That was until the eleventh game – and the most crucial game of del Potro’s French Open journey this year – when he fashioned three break points and took the second of them.
A hold to love later and the Argentine booked his date with destiny on Friday.