Argentine international Gabriel Mercado bundled home the winner as Sevilla moved up to second in La Liga with a 1-0 win over fierce local rivals Real Betis on Tuesday.

Mercado's first goal for the club from on-loan Manchester City midfielder Samir Nasri's free-kick continued the Europa League holders' four-year unbeaten run in the Seville derby in La Liga.

Betis were right to feel aggrieved just moments after Mercado's 51st minute winner, though, when Alex Alegria had an equaliser wrongly ruled out for offside against Ruben Castro.

Nasri had the clearest opening before the break, but fired straight at Antonio Adan after a mix-up between the Betis 'keeper and his defence allowed the Frenchman a free effort on goal inside the area.