Karolina Pliskova hadn't reached the second week of a Grand Slam tournament before competing at this year's US Open but the 10th-seeded Czech is now riding on an impressive 11-match winning streak since winning the biggest title of her career in Cincinnati.
Pliskova was competing under the lights in the Arthur Ashe Stadium in a partisan crowd firmly behind the world number one Serena Williams.
However, Pliskova was used to that atmosphere and saving a match point in her fourth round victory over Williams' sister, Venus.
The Czech's straight sets victory means that Australian Open champion Angelique Kerber is the new world number one, ironically, Pliskova prevented the German from achieving this feat by defeating her in Cincinnati.
Pliskova settles and cruises in the opening set
The 10th seed won the coin toss and elected to receive as she was trying to get the early break on Williams' serve, however, the American held in the opening game to love.
Pliskova responded with a hold of her own to level the match at 1-1, immediately in the third game, Williams had a commanding 30-0 lead but four consecutive points from the 10th seed allowed her to take the initiative and take the early break leading 2-1.
The reigning Western and Southern Open champion consolidated the break with a couple of aces, and a backhand unforced error out wide from an erratic Williams allowed the Czech to settle down into this contest.
In the fifth game, the 22-time Grand Slam champion was under pressure on her serve starting the game with a forehand unforced error out wide, and a double fault but the American managed to get a couple of winners to get the game leveled at 30-30.
Pliskova created another break point with a forehand volley at the net for the double break, however, Williams won three consecutive games with an ace down the T but trailed 2-3.
The Czech had a little more trouble on her serve in the sixth game serving a couple of double faults, but unforced errors from Williams' racquet helped Pliskova extend her lead to 4-2.
However, in the seventh game of the first set, an out of sorts Williams opened the game with a double fault followed by two backhand unforced errors, and the Czech successfully gained the double break, breaking the American's serve to love by virtue of a forehand unforced error into the net.
Pliskova did not look fearless and she played like a player who had all of the experience under her belt, however, a good serve down the middle gave the 10th seed the opening set in 26 minutes by a tidy 6-2 scoreline.
Close second set
This year's reigning Wimbledon champion started the second set slowly, and Pliskova at 30-40 created a break point by virtue of a forehand unforced error in the net by Williams, however, a backhand unforced error sailing long from Pliskova's racquet let Williams off the hook.
An ace out wide and a forehand winner in the corner gave Williams the hold she needed, although, Pliskova once again responded with a hold of her own to level the second set at 1-1.
Williams and Pliskova both held their next service games to have the match leveled at 2-2, however, there were more problems for the American on serve.
The American gained a 30-15 lead on her serve but three consecutive errors from Williams' racquet, handed Pliskova the crucial break to lead 3-2 and a set up.
Pliskova had the finishing line in sight but Williams was intent to get the immediate break back with a backhand winner down the line, followed by a double fault and two unforced errors from Pliskova allowed Williams to break the lanky Czech's serve to love for the first time in the match.
Tiebreak to settle the match
The world number one almost gave Pliskova the immediate break advantage again by starting the seventh game with untimely back-to-back double faults, however, Williams would win the next three points with an ace out wide to bring up a game point.
A couple of erratic errors from Williams handed Pliskova the chance to gain the ascendency again but the Czech was unable to capitalize with a forehand unforced error sailing wide.
Williams was able to get out of that service game unscathed with a couple of more errors from Pliskova's racquet to lead 4-3 in the second set.
Pliskova held to 30 to level the second set at 4-4, followed by a comfortable service game to love for Williams.
The Czech had the pressure of serving to stay in the set but passed the test with flying colors with a sweet forehand dropshot winner at the back of the court to hold to 15, however, she got a warning for coaching from her coach appearing to signal instructions.
The top seed held comfortably to put the pressure back on Pliskova who had the task of serving to stay in the second set once again at 6-5.
Williams started the game with a backhand winner punishing Pliskova's second serve but the Czech responded with two good first serves down the middle, and Pliskova was two points away from losing the second set with a forehand unforced error.
However, Pliskova was able to hold onto her serve with an impatient Williams failing to capitalise on the Czech's second serve and an ace out wide followed by a roar, got the second set easily poised at 6-6 and the destination of the second set was to be decided in a tiebreak.
Pliskova reaches maiden Grand Slam final
The Czech quickly built up a 3-0 lead in the tiebreak as the American began the tiebreak with a backhand unforced error coupled with two more errors from her racquet.
However, Pliskova's 3-0 lead quickly evaporated with two tight unforced errors from the Czech and a double fault had the tiebreak evenly poised at 3-3 at the changeovers.
Williams was able to gain a mini-break and lead in the tiebreak for the first time with a scintillating backhand winner down the line, however, Williams' mini-break advantage was short-lived with a double fault and a gutsy winner down the line handed the 22-time Grand Slam champion a 5-4 lead.
The American was unable to build on that lead, and Pliskova was serving but a forehand unforced error out wide and a backhand unforced error sailing long gave Pliskova a match point.
Pliskova didn't hesitate and took the match point at the first time of asking with Williams serving a double fault, and the 10th seed reached her first Grand Slam final at the US Open with a 6-2, 7-6 (5) victory in 1 hour and 25 minutes.
Match stats
The big-serving Czech got 56 per cent of her first serves in and won 84 per cent of the points on her first serve, and converted three out of the six break point chances she created.
The 10th seed produced 19 winners and committed 25 unforced error, whilst Williams got 53 per cent of her first serves in and won 66 per cent of the points on her first serve.
31 unforced errors and 20 winners came from the American which was an under par performance for her.
This will be a disappointing loss for Williams as she relinquishes her world number one ranking and loses in the semifinals in New York for the second consecutive year.
Pliskova becomes the first Czech woman since Helena Sukova in 1993 to have reached the final at Flushing Meadows.
Next for Pliskova
The 10th seed will be competing in her first US Open final on Saturday, and she will face the second-seeded Australian Open champion Angelique Kerber.
Pliskova became the eighth player to defeat Serena and Venus Williams in the same tournament, and this could be an omen for Pliskova as Kim Clijsters achieved this feat at the US Open in 2009 by defeating Venus in the fourth round, Serena in the semifinals and went on to win the title.