Kyle Edmund failed to reach the first ATP final of his career after going down to a three-set defeat to Ryan Harrison at the BB&T Atlanta Open.
Edmund won the first set tie-break but Harrison rallied to win the remaining two sets to book a date with fellow American John Isner in Sunday's final after the 6-7 (7/5) 6-3 6-4 win.
Edmund broke Harrison as he was serving for the first set and carried that momentum into the tie-break to take the set.
But Harrison recovered and raced into a 4-1 lead in the second set to level the match.
Harrison won eight of the final nine points of the match, breaking Edmund to love at 4-4 and secured victory when the Brit drove a forehand wide.
Isner saw off Gilles Muller 6-4 6-2 in the other semi-final.
Leonardo Mayer is odds-on to become the second straight lucky loser to win an ATP World Tour title after booking his place in the final of the German Open in Hamburg on Saturday.
Mayer beat Federico Delbonis 6-3 7-5 to set up a meeting with namesake Florian in what will also mark the first tour final between two players ranked outside the top 100 since 2013.
Leonardo has been chalked up as the 4/7 favourite by Sky Bet with Florian offered at 11/8.
Leonardo has not looked back since being granted his second chance after losing to German wild card Rudolf Molleker last Sunday.
The 30-year-old Argentinian served strongly to see off compatriot Federico Delbonis in one hour and 24 minutes, breaking his opponent twice in the final set to earn the fourth final appearance of his career.
He will be looking to follow the example set by Russian Andrey Rublev, who also bounced back from a qualifying defeat to win the Croatia Open in Umag last week.
Home favourite Florian Mayer booked his own place in the final when opponent Philipp Kohlschreiber retired due to injury while leading their all-German showdown 6-4 2-3.
Mayer was broken twice to drop the first set and the pair traded early breaks in the second before an evidently-frustrated Kohlschreiber was forced to call it a day.
German qualifier Yannick Hanfmann continued his own dream run as he saved four match points on his way to reaching the final of the Swiss Open in Gstaad.
Playing in only his third main draw event, the world number 70 came from a set down and squeezed through a tight second set tie-break to see off sixth seed Robin Haase 3-6 7-6 (8/6) 7-6 (7/4).
In a match lasting just under two and a half hours, Hanfmann saved his first two match points in the second set tie-break then two more as he served to stay in the match at 5-6 in the decider.
In the final Hanfmann will face fourth seed Fabio Fognini after the Italian also came from behind to beat Spanish second seed Roberto Bautista Agut 5-7 6-2 6-3.
Fognini is the 1/3 favourite for the final with Hanfmann 5/2 for the upset.
