Dec 10 (Reuters) - Lewis Hamilton pushed Formula One rival Max Verstappen off the top of the timesheets to end the opening day of practice for their title showdown at the Abu Dhabi Grand Prix comfortably fastest. The Briton lapped the revised 5.2-km long Yas Marina track in one minute, 23.691 seconds, the only driver to drop below the 1:24 mark with his 24-year-old Dutch rival fourth. The Red Bull driver had lapped fastest in Friday afternoon"s opening session of track action with Hamilton, whose quickest lap time was deleted, third. But, the Dutchman could get no closer than 0.641 seconds off the Briton"s benchmark in the evening, though he did appear to have the edge over Hamilton during the heavy-fuel race simulations. "It’s been a relatively decent day," said Hamilton, while praising the changes made to the Yas Marina track in order to boost overtaking and give it a more flowing feel. "We got through our sessions and still a bit unknown in terms of pace but I’m sure it’s going to be super-close like it has been in the previous races." Verstappen and Hamilton head into Sunday"s race, a winner-takes all showdown, level on points. But the Dutchman is ahead 9-8 on wins and will become champion if neither score. The pair have already collided three times this season, raising concerns that a thrilling title battle might end in a crash. But the governing FIA has warned drivers of severe consequences, such as a points deduction, for unsportsmanlike behaviour. Verstappen, winner from pole position in last year"s Abu Dhabi finale, acknowledged his Red Bull lacked single-lap speed but was encouraged by his race pace. "We’re still learning and understanding a few things," he said. "But clearly the short run didn’t go to plan, lacking a bit of pace, but I think the long runs were quite a bit more competitive. Alpine"s Esteban Ocon took advantage of the Red Bull"s relative lack of outright speed, going a surprise second fastest, 0.343 seconds adrift of Hamilton. Valtteri Bottas in the other Mercedes was third, 0.392 seconds off the pace. Kimi Raikkonen crashed in the closing minutes of the session, with the resultant red flag bringing an early end to running. The Finn, heading off into retirement on Sunday, lost control of his Alfa Romeo at the left-handed Turn 14 and spun into the barriers. The 42-year-old, who ended the session 16th, walked away from the shunt but his Alfa Romeo was a mangled mess. "Yeah, I lost the rear," he said over the team radio in typical deadpan style. Sergio Perez was fifth in the other Red Bull ahead of Alpine"s Fernando Alonso and Japanese rookie Yuki Tsunoda in his AlphaTauri. Charles Leclerc was eighth ahead of Ferrari team mate Carlos Sainz. Frenchman Pierre Gasly in the other AlphaTauri rounded out the top 10. Williams reserve Jack Aitken replaced Mercedes-bound George Russell in the opening afternoon session just five months after having suffered a broken collarbone and fractured vertebra at the Spa 24 hours sportscar race in Belgium and set the 17th-fastest time. The second session, which began at the same time as Saturday"s qualifying and Sunday"s race are scheduled to start, offered up a more representative picture of the pecking order.