Despite a first-round loss at the Miami Open to the in-form Naomi Osaka, Serena Williams has her eyes firmly looking forward as she makes her comeback from maternity leave.

"Every tournament is an opportunity for me to better understand the areas I need to improve to be my best," Williams said in a statement after Wednesday's match, won by Osaka, 6-3, 6-2. 

The defeat was the earliest that the eight-time champion had ever been dealt in Miami, having reached at least the fourth round in 16 previous appearances.

"Naomi played a great match and I learn something each time I play. I look forward to continuing my return by progressing every day," she continued.

"I'm so grateful for my fans who continue to support me every step of this incredible journey." 

Later, the 23-time Grand Slam champion expounded on her second tournament back in an Instagram post.

In the post, she added: "[Four] months ago I could not walk to my mailbox...but I will keep going forward and I'll get there."

The former World No.1 scored two wins last fortnight in Indian Wells, defeating Zarina Diyas and Kiki Bertens before falling to sister Venus in the third round.