In the last twenty years, the paradigm that has dominated the discipline of language teaching is the SLA theory and Krashen's five hypotheses which are still proving flexible to accommodate earlier reforms. This paper reviews second language acquisition (SLA) theory to establish an understanding of its role in the EFL/ESL classrooms. Other areas of SLA theory, particularly Krashen's five Hypotheses are being reviewed to provide a brief overview of SLA research in relation with Krashen's views. This paper, considering the importance of SLA theory, makes an attempt to find out how the shift in the language teaching techniques can be correlated and connected to the conceptual framework of the SLA theory.