Magnus Carlsen's indomitable fighting spirit glowed as he bounced back with a resounding must-win victory over young Vincent Keymer to remain in the hunt for the elusive FIDE World Cup title Thursday in Baku, Azerbaijan.

In the brink of early elimination, the 32-year-old, five-time classical world champion from Norway summoned all his energies in defeating the 18-year-old German to tie his Round 4 match at 1-1.

Carlsen and Keymer were fighting to the death as of press time, using faster and shorter time controls like nine other individual match-ups.

Attacking early on the eighth move with the most aggressive variation of the Ruy Lopez against the old Murphy line of defense, Carlsen threw everything at Keymer, castling opposite on the queenside.

The prodigious Keymer, however, missed a combination — a brilliant knight sacrifice on the 17th move — that would have gained him an extra pawn and possibly the match. Instead, Carlsen continued to plod on and win.

A clearly off-form Filipino-American Wesley So, who is seeded sixth, bid farewell to his title campaign as he was stopped in his tracks with a draw after losing in the opening match Wednesday.

The 38th seed Alexey Sarana of Serbia came prepared against the sharpest lines and forced a positional draw against So's Gruenfeld defense.