Match detailsFixture: (3) Dominic Thiem vs (5) Alexander ZverevDate: 8 May 2021Tournament: Mutua Madrid Open 2021Round: SemifinalsVenue: Madrid, SpainCategory: ATP Masters 1000Surface: Red clayPrize money: €2,614,465Match timing: Not Before 4 pm local time, 7.30 pm ISTLive telecast: USA - Tennis Channel | UK - Amazon Prime VideoDominic Thiem vs Alexander Zverev previewDominic Thiem will square off against Alexander Zverev in the semifinals of the 2021 Mutua Madrid Open on Saturday, in what will be a rematch of the 2018 final.Thiem came from a set down to oust John Isner in the quarterfinals on Friday; the Austrian won 3-6, 6-3, 6-4. Zverev, on the other hand, sent Rafael Nadal packing in straight sets with a 6-4, 6-4 scoreline.Thiem had no answer for Isner's missile-like serve in the opening set. The Austrian could muster just three points on his opponent's serve as he went down 3-6 in almost no time.Thiem to the semis!@ThiemDomi makes the #MMOPEN semi-finals after outlasting Isner 3-6, 6-3, 6-4 👏 pic.twitter.com/43VR5BVmPY— ATP Tour (@atptour) May 7, 2021Early in the second set, it seemed that Isner would complete the upset as he held four break points at 2-2. But Thiem held his nerve as well as his serve to nose ahead, before finally getting a read on the American's serve in the very next game. The Austrian broke Isner to love and went on to win the set.Isner's serve dipped in the decider, and Thiem took full advantage of that with some excellent returns. The 27-year-old broke Isner decisively at 4-4 before easily closing out the match.Alexander Zverev, meanwhile, caused the upset of the tournament by ousting five-time champion Rafael Nadal in straight sets. Zverev played at a very high level throughout, but he was also helped by the fact that Nadal was nowhere close to his best.It's a first win on clay against Nadal for @AlexZverev! 👏 He defeats the five-time Madrid champion 6-4, 6-4 and moves into the semi-finals. #MMOPEN pic.twitter.com/neyKUu3ONd— ATP Tour (@atptour) May 7, 2021The 2018 champion made full use of Nadal's shortcomings, especially off the serve and forehand. Zverev unleashed 28 winners compared to Nadal's six, and ended up winning the match at a canter.Dominic Thiem vs Alexander Zverev head-to-headDominic Thiem leads Alexander Zverev in the head-to-head by a margin of 8-2. Even in the claycourt meetings, Thiem has a huge lead of 4-1.That said, the German's sole win over Thiem on clay came right here at Madrid. Zverev defeated Thiem in the 2018 final to win his third career Masters title.Dominic Thiem vs Alexander Zverev predictionAlexander Zverev after defeating Rafael NadalAlexander Zverev's height and long levers are his biggest weapons, and they are particularly useful in the high-altitude conditions at Madrid. The German has been timing his returns impeccably in the Spanish capital, and the results of that are evident.Zverev has been able to find winners from virtually every part of the court this week. The 24-year-old has had success both while taking the ball on the rise and while hitting from the behind the baseline, which has made him a very difficult player to defend against.Dominic Thiem, on the other hand, is yet to hit top gear, and isn't striking the ball with his usual ferociousness this week. On his day the Austrian has the raw power to outhit Zverev, but the fact remains that he is still not at his best after his recent physical and mental struggles.Zverev has shown more consistency in all departments so far in Madrid, which makes him the favorite for Saturday's fixture.Prediction: Alexander Zverev to win in three sets.