Social factors play a critical role in motivating player participation and commitment to online multiplayer games. Many popular mobile massively multiplayer online games (MMOGs) adopt social network embeddedness (SNE) functions to optimise players' social play experience. SNE changes the traditional pattern of MMOG social play by porting acquaintance relationships (e.g., Facebook friends) from social networking sites to the virtual game world. However, little understanding exists on how SNE impacts mobile MMOG players' game participation results such as play performance and play frequency. Drawing on the affordance framework and social capital literature, this research proposes a theoretical model that integrates the factors of SNE technology affordance (identity transparency and information transparency), players' social experience (social interaction, social support, shared vision, and social pressure), plus affordance effects (play performance and play frequency). The model was validated through a longitudinal field study, in which both subjective and objective data were collected from Game for Peace players. Our findings indicate that identity transparency and information transparency positively correlate with social interaction, social support, shared vision, and social pressure, which, taken together, significantly affect play frequency. The results also show that social interaction and shared vision positively impact players' play performance. The study enhances the theoretical understanding of social relationships in players' game participation results from the SNE aspect. Finally, we lend insights on how game operators can improve player game experience and stickiness.