Magnus Carlsen’s erratic form since his 30th birthday a month ago suffered another dip on Wednesday when Russia’s Daniil Dubov used his mazy tactical skills to eliminate the world champion from the quarter-finals of the $200,000 online Airthings Masters and enhance the 24-year-old Muscovite’s own growing status as a creative and swashbuckling crowd favourite. In the other quarter-finals, Levon Aronian (Armenia) beat Hikaru Nakamura (US), Teimour Radjabov (Azerbaijan) beat Ian Nepomniachtchi (Russia), and Maxime Vachier-Lagrave (France) beat Wesley So (US). The semi-finals continue at 2pm on Friday with live grandmaster commentary on chess24.com, Radjabov won the first set (of two, with possible tie-breaks) 3-1 against Dubov while Aronian leads Vachier-Lagrave by the same score. The world champion’s form has dropped off since his 30th birthday a month ago, when a Tour publicity photo showed him with a tropical sea as background and a tray full of gourmet delights. While Dubov modestly attributed his success to luck, Carlsen called it a “collapse” and added: “I’m in a deep funk right now.” In the game which eliminated the Norwegian, the decisive error which changed a difficult win a piece ahead into a speedy loss with checkmate in the final position came at move 34 when Qe7 lost while the active Qa5! would have won. Dubov now has a large plus score against Carlsen in their online tournament games during the pandemic, leading 6-3 with four draws. Yet the Russian’s overall form does include down days, so that he has yet to reach the top 10 across the board or to get near qualifying for the world title candidates. This week’s results put extra pressure on Carlsen for the next major over-the-board tournament at Tata Steel Wijk aan Zee, starting in the Dutch seaside resort on 15 January. Carlsen has an outstanding record at Wijk, where his 13 opponents include the world No 2, Fabiano Caruana, who has kept a low profile in the online Tour, plus the two rising stars Dubov and Alireza Firouzja. Meanwhile, the online British championship will have its final two rounds on Saturday and Sunday (7pm start, go to chessbomb.com to watch the games). The England No 1, Michael Adams, leads with 6/7, half a point ahead of Matthew Turner. Adams has won seven British titles across the board, but his chances of equalling Jonathan Penrose’s record of 10 wins are diminished because the online version will not count in official titles. The most eye-catching performance has been in the women’s championship. Ketevan Arakhamia-Grant, who in her peak years was a world-class player, won all seven games, but second with 5/7 was Nina Pert, aged 12 with a 1537 rating. The Brentwood schoolgirl, daughter of IM Richard Pert and niece of GM Nick Pert, defeated the No 2 seed in the final round and has a bright future.