at four games all.
Then with the Serbian serving to stay in the set at 4-5 30 all, Alcaraz struck a down the line backhand winner which he followed up with a crosscourt forehand winner to break serve and close out the set.
At two all in set two with Alcaraz serving, Lajovic struck several powerful forehands to reach breakpoint.
Alcaraz netted a crosscourt forehand to drop serve and trail 2-3.
In the following games Lajovic took leads of 4-2 and 6-5.
Serving for the set at 6-5 30 all, Lajovic struck a crosscourt forehand volley winner to reach set point at 40-30.
Alcaraz struck a crosscourt backhand volley winner to save set point before hitting an overhead winner to break serve and reach the tiebreaker.
In the tiebreaker the 32 year old 80th ranked Lajovic struck five consecutive forehand errors to trail 0-5.
Lajovic then hit a crosscourt backhand long to face match point at 0-6.
The 19 year old second ranked Alcaraz struck an inside out crosscourt forehand winner, his 23rd forehand winner of the match to close out the tiebreaker and the match after one hour and 54 minutes of play.
After winning the title in Buenos Aires last week in his first tournament of the year following an abdominal injury, yesterday's victory was Alcaraz's seventh win in a row.
In today's semifinals, Alcaraz takes on the unseeded qualifier Jarry Nicolas of Chile. The two players have never faced each other before.