Rafael Nadal will hope to put early-season injury issues behind him when he returns to action in Acapulco
Rafael Nadal starts his bid for the title on Tuesday evening as John Isner became the first big name early casualty in Acapulco, losing to Ryan Harrison.
Eighth seed Isner was beaten in straight sets by his fellow American and Harrison advances to face either Diego Schwartzman or Fernando Verdasco in the last 16 - the pair face off on Tuesday just a couple of days after Schwartzmann won their Rio Open final in Brazil.
Spanish veteran David Ferrer, South Africa's Kevin Anderson and another American, Jared Donaldson, were among Monday's other first-round winners but attention now switches to a blockbuster day's play on Tuesday.
Nadal's return to action is the headline event and he is joined by Juan Martin del Potro, Alexander Zverev and Dominic Thiem, who faces Britain's Cameron Norrie.
Top seed Nadal has not featured since injury ended his Australian Open bid at the quarter-final stage against Marin Cilic and is slated to be the third match on Cancha Central when he takes on fellow Spaniard Feliciano Lopez.
Nadal, twice a winner of this event, has seen Roger Federer regain the world No 1 spot while he has been forced to watch on, but he insists his priority is playing tennis not the rankings battle.
Nadal was forced to retire from his Australian Open quarter-final with Marin Cilic
"At this point in my career, I'm looking to be happy, and play in the proper weeks, whether No 1 or No 5 in the rankings," he said.
"I took a couple of weeks of rest and worked hard on rehabilitation, last week I started practising hard again. I feel ready."
Del Potro gets the men's action underway, with his match against Mischa Zverev scheduled for no earlier than midnight following the women's match between Sloane Stephens and Pauline Parmentier.
The final match on the main court sees Zverev's younger brother and world No 5 Alexander in action as he looks to get his stop-start season going against Steve Johnson.
British focus will be on Norrie who impressed hugely in the Davis Cup defeat to Spain earlier this month and having reached the main draw, he has the match sharpness he will need against third seed Thiem.
Cameron Norrie will look to bring his Davis Cup form to the main tour as he faces Dominic Thiem
The Austrian clay-court specialist won a title in Buenos Aries a couple of weeks ago and was a beaten quarter-finalist in Rio last week, but he will give Norrie a tough test.
The world No 113 beat Roberto Bautista Agut in the Davis Cup but Thiem, on clay, represents the toughest test of his career to date.
Perhaps the most eye-catching match of the day sees Kei Nishikori continuing his return, the former world No 4 plays Canadian teenager Denis Shapovalov while fourth seed Jack Sock and Korea's Hyeon Chung are also in action.
Follow the action from Acapulco on Sky Sports Action and Main Event from midnight and keep up to date with the latest from Dubai and Acapulco on www.skysports.com/tennis with news, previews, live blogs, reports and expert analysis.
The Tie Break Tens is back and ready to take New York City by storm when it hits Madison Square Garden. Serena and Venus Williams will compete at the All-Women tournament and you can watch it live on Sky Sports Main Event and Sky Sports Mix from midnight on Monday.
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