The high sampling rate in Wi-Fi is set to support bandwidth-hungry applications. It becomes energy inefficient in the post-PC era in which the emerging low-end smart devices increase the disparity in workloads. Recent advances scale down the receiver's sampling rates by leveraging the redundancy in the physical layer (PHY), which, however, requires packet modifications or very high signal-to-noise ratio (SNR). To overcome these limitations, we propose Sampleless Wi-Fi, a standard compatible solution that allows energy-constrained devices to scale down their sampling rates regardless of channel conditions. Inspired by rateless codes, Sampleless Wi-Fi recovers under-sampled packets by accumulating redundancy in packet retransmissions. To harvest the diversity gain as rateless codes without modifying legacy packets, Sampleless Wi-Fi creates new constellation diversity by exploiting the time shift effect at receivers. Our evaluation using GNURadio/USRP platform and real Wi-Fi traces have demonstrated that Sampleless Wi-Fi significantly outperforms the state-of-the-art downclocking technique in both decoding performance and energy efficiency.