Iga Swiatek said she had surprised herself with her ‘mental toughness’ after beating Naomi Osaka 6-4 6-0 at the Miami Open final.
The 20-year-old Pole is just the fourth woman to complete the double which also includes the Indian Wells event.
It is the third tournament she has won in a row on the WTA 1000 circuit, the first time any woman has done that at the start of a campaign, and takes her to 17 consecutive victories.
Speaking before the match Swiatek had admitted to some tiredness but she was carried through as she was ‘energised’ by success.
Afterwards, she admitted to more than one doubt.
“These weeks were so intense I didn’t really know if I would able to keep up with the streak that I have,” she explained.
“It’s amazing for me that I could show mental toughness because my whole life I thought I could do more and sometimes I was losing and I didn’t even know why.
“This season I feel like everything clicked so it’s great and I am really happy.”
Swiatek will become the world No. 1 on Monday following the retirement of Ashleigh Barty.