The Spaniard would have been headlining the evening’s action at the O2 Arena had he not withdrawn from the competition on Monday with a knee injury after defeat to David Goffin.
His retirement offered Carreno Busta the opportunity to play two matches as opposed to the solitary encounter often afforded an alternate, just as Goffin himself had last year.
But Spaniard could not capitalise on the chance to spring an upset despite a faltering Thiem who has played more tournaments than any other top-10 player in 2017 and looked every bit weary for it, leaving the Spanish fans who had bought tickets for Nadal disappointed by their countryman’s result.
“It was a very tough match,” Thiem said.
“He took the place of Rafa very well and again it was a very tough three-setter, I’m very happy to be through and it got very tight at the end.”
Carreno Busta came into the match with a curious record against Thiem, having lost all four top-level meetings but having garnered at least a set on all but one occasion.
Their only meeting on hard courts was at the US Open last year when the Austrian lost the first set 6-1 only to bounce back and win in four.
But a comeback never looked necessary as his single-handed backhand found its range well early on and when Carreno Busta twice found the net in baseline rallies, it handed Thiem a break and a 3-2 lead.
The crowd seemed largely unengaged, apart from the odd “hilarious” cry of “come on, Rafa” and a number of disagreeing efforts to mispronounce Thiem’s surname.
And when Thiem secured the set with a second break after just half an hour, the stereo pumping “I’m Blue” seemed appropriate. This wasn’t “after the Lord Mayor’s show” stuff. The Lord Mayor hadn’t even turned up.
Thiem was almost apologetic to be winning, holding love at the start of the second set and trying to bounce on his toes at the end of the court to stop himself falling into a lull.
And so it proved, as he let slip a 40-0 lead at 1-1 to deuce, before a fine Carreno Busta backhand return was too hot to handle. He swatted a forehand well wide and was, out of nowhere, a break down.
The Spaniard immediately had to save break points and gave Thiem a long hard look as if to say “I’m not Rafa, but I’m not going away”. It was perhaps the needle the higher ranked man needed but Carreno Busta’s defence remain difficult to penetrate, with only the very fiercest of forehands and flattest of backhands finding a rare path through. It was draining for his opponent to try and break him down and after a long season, he barely looked able to muster the energy to do so.
When Thiem came to serve to stay in the second set, Carreno Busta three times battered whistling return winners out of the deuce court, two across his opponent’s face and the third down the line. Thiem’s 14th unforced error of the set sealed it.
But the clumsiness appeared to be catching, as the Spaniard double-faulted in the first game of the decider and Thiem was able to break for a third time.
And while Thiem continued to show an impatience born out of tiredness, Carreno Busta showed the kind of energy we are more used to seeing from his stricken countryman. It eventually told as he broke back in the sixth game to the horror of Kristina Mladenovic, in Thiem’s box alongside his mother. More pain was painted across their preferred player’s face when he saw four break points saved a game later.
However, Thiem was not to be denied, Carreno Busta’s spirited defence and punctuating aggression was not enough and after 126 minutes, the Austrian finally dragged himself over the line.