Sisinio González MartÃÂnez (; born 22 April 1986), commonly known as Sisi , is a Spanish former professional footballer who played as a left winger. He is currently technical assistant of Segunda División club Real Valladolid.
Sisi was born in Albacete, CastillaâÂÂLa Mancha. A product of Valencia CF's youth system â he arrived aged 15 from his hometown side Albacete Balompié â he first served loan stints in the Segunda División, with Hércules CF and Real Valladolid, with a 2007 top-flight promotion with the latter (he also appeared in the Segunda División B with the former). Whilst playing with Valladolid, the football site Goal.com mentioned him as one of the emergent talents in Spain.
In July 2008, Sisi was sold by Valencia to La Liga club Recreativo de Huelva. Midway through his only season he was diagnosed with hepatitis A, being rendered unavailable for two months; he made his return as a substitute on 4 April 2009, in a 0âÂÂ1 home loss against Andalusia neighbours Sevilla FC.
On 24 August 2009, after Recres relegation, Sisi returned to Valladolid, signing a three-year contract. He scored on his debut in a 2âÂÂ1 win at Real Zaragoza, but was injured through most of the campaign and suffered relegation for the second consecutive time.
Sisi scored a career-best five goals in 2011âÂÂ12 (from 36 appearances) as the Castile and León side returned to the top flight after two years. In the subsequent off-season he joined CA Osasuna, being hindered by two severe knee injuries during his spell, the last one contracted after only five minutes of the home fixture against FC Barcelona.
In the summer of 2015, aged 29, Sisi moved abroad for the first time, joining Suwon FC in the K League Challenge. In the following transfer window, he reunited with former Osasuna boss Jan Urban at Lech Poznaà  after agreeing to a six-month deal.
On 25 August 2016, Sisi signed a one-year contract with Veria FC. Until his retirement, he competed exclusively in Japan's J2 League.
In the 2003 FIFA U-17 World Championship, Sisi was a key element for Spain, who finished runners-up to Brazil (1âÂÂ0). FIFA described him in their technical report as a "...well-developed technique and ball control, fast and agile", as he was listed amongst the nation's Talented Players list.
Two years later, Sisi appeared against France in the 2005 UEFA European Under-19 Championship, as the national team failed to qualify for the final stages in Northern Ireland, losing 1âÂÂ0 in the elite round. In 2007, he progressed to the under-21s.
On 7 June 2024, having previously worked as Beñat Labaien's assistant at Tokushima Vortis, Sisi returned to Valladolid as manager of the Juvenil B squad. He was promoted to the Juvenil A in February 2025, before becoming a part of Guillermo Almada's staff at the senior first team as a technical assistant.
On 15 December 2025, after Almada expressed his interest in leaving for Real Oviedo and was subsequently suspended by Valladolid, Sisi was appointed caretaker manager of the main squad. On his second-tier debut four days later, they lost 3âÂÂ0 at SD Eibar.
Valladolid