So winning his match against frequent Davis Cup teammate David Ferrer in two quick sets was likely his first preference. The Spaniard's last choice would probably have been to lose a marathon.
He finished somewhere in between, defeating Ferrer -- but in nearly three hours, 6-7 (2-7) 6-3 6-4 -- to conclude the round-robin stage 3-0 in London just as his longtime rival Roger Federer did Thursday.
It was a tricky situation for Nadal. If he lost quickly, he would have plenty of energy for world No. 1 Djokovic, who has beaten the 14-time grand slam winner in seven of their last eight meetings and captured three majors this season.
But mentally, he wouldn't enter the clash with the "positive" feelings he spoke of after seeing off two-time grand slam champions Stan Wawrinka and Andy Murray in straight sets earlier in Group Ilie Nastase.
Later Friday, Wawrinka fended off home hope Murray 7-6 (7-4) 6-4 and will face off against six-time ATP champion Federer -- his Swiss compatriot -- in Saturday's second semifinal.
While Nadal was expected to get the better of Ferrer, his recent head-to-heads with Djokovic make the Serbian a substantial favorite on Saturday.
Certainly Nadal's celebration after outlasting the already-eliminated seventh seed -- he clenched his fists and looked skywards -- suggested Friday's affair meant more to him than what would usually be the case with a dead rubber.
He confirmed as much in his briefing with reporters in a year in which he didn't win a grand slam for the first time since 2004 and suffered a string of upset losses.
"It's an important victory, doesn't matter if I was already qualified," said Nadal. "For me the main goal is to try to arrive in good shape next year.
"Today was an opportunity to play against another top-eight player in a tough surface.
"I think I competed well. Three straight wins against top-eight players, that's great news for me."
Oh, a dead rubber with $167,000 -- the amount received by the victor in a group match -- at stake. If Nadal wins the ATP title for the first time, the two-time runner-up will take home $2.23 million.
Assuming Nadal can recover well enough physically, the contest against Djokovic could be their closest meeting this year -- the 28-year-old defending champion has won all seven sets in the three matches they've contested in 2015.
Indeed it's been a difficult year overall for former No. 1 Nadal, but he has had an encouraging past couple of months. A win over Djokovic would be his biggest win of the season.
"Let's see what's going to happen," Nadal said. "But I am very happy about what I did in the last five weeks of the season. I finish the season the way that I really want to start the next one."
Nadal's recent upturn hasn't gone unnoticed by Djokovic.
"First couple of matches he played here against Wawrinka and Murray showed that he feels more confident, shows that he's starting to miss less, serve efficiently, use his forehand much better," Djokovic told reporters Thursday.
"I know that, I've been watching. I know what (to expect). We played so many times," added Djokovic, 22-23 lifetime versus Nadal.
If Nadal has fared better in the first three games of a hard-court match against an elite opponent than on Friday afternoon, it can't have been on many occasions.
Nadal came out aggressive and connecting, zipping winners down the line, at the net and bludgeoning cross-court forehands. In building a quick 3-0 double-break lead, he hit five winners and at one stage tallied 10 straight points.
A blowout seemed like a possibility.
Perhaps Nadal was playing too well, at a level he was never going to maintain. When Ferrer lifted his game, suddenly it became a battle that many expected.
Even though Nadal led their head-to-heads 23-6, which included winning the 2013 French Open final, they were tied 4-4 on hard courts.
It was Ferrer who ended Nadal's hopes of the "Rafa Slam" -- triumphing at four straight majors -- at the 2011 Australian Open, prevailing when his friend was hampered by a hamstring injury early in the first set.
Ferrer surged to 16 of 20 points in the next four games to build a 4-3 lead at the O2 Arena. The topsy-turvy nature ensued, and Nadal had the set on his racket after breaking for 6-5.
Earning a set point after escaping a 0-40 hole, a short, looping Nadal forehand -- the kind he had been offering up less and less during his revival -- was punished by Ferrer. The latter later broke and took the first three points of the tiebreak to seize control.
Nadal hit only two more winners in the first set following the third game, and made 18 unforced errors.
Ferrer, who remains one of the game's best returners, was unable to muster a break point in the second set and Nadal's mounting pressure paid off in the eighth game, when a solid return helped him to break for 5-3.
Once again Ferrer was in trouble. In a nearly 14-minute first game of the third -- highlighted by a stunning lob from Ferrer that drew praise from his opponent -- Nadal carved out five break points. Ferrer saved all of them.
But Ferrer hasn't been able to win the big points this tournament -- the 33-year-old led Wawrinka 5-2 in the first set Wednesday prior to succumbing 7-5 6-2 -- and the trend continued.
With Ferrer leading 4-3 on serve, Nadal creaked on serve in the eighth game, falling behind 0-30. He hung on. Nadal broke in the next game, powering a forehand down the line. A final twist didn't materialize.
Nadal applauds opponents after matches he wins when it's been a dogfight, so it wasn't a surprise when the gesture resurfaced.
He wouldn't mind doing the same thing Saturday.
Wawrinka, this year's French Open champion, had won two straight against Murray. He possesses the firepower to hit through the Scot's fine defense -- and did it again.
Murray, however, imploded when he led 4-2 in the first-set tiebreak.
In the second, Wawrinka nearly blew a 5-2 advantage. He saved two break points in the final game, when Murray drew boos for breaking his racket and a nervy Wawrinka struggled to land a first serve.
Wawrinka thus finished second in the group with a 2-1 record; Murray was 1-2. He can now focus on the Davis Cup final.
If Wawrinka's match with Federer is as dramatic as their semifinal in London last year, fans are in for a treat. Federer saved four match points in a 4-6 7-5 7-6 (8-6) win, with his wife Mirka taunting Wawrinka
late in the third.