Stock futures were struggling for direction on Thursday as investors ditched tech and rotated into blue-chips, with the Dow Jones Industrial Average on track for a fourth straight closing high.

Sandisk sank 8.8% in premarket trading after the memory-card maker's disappointing outlook overshadowed strong results for its fiscal fourth quarter.

Western Digital tumbled 14% ahead of the opening bell after the hard-drive maker also provided so-so guidance that failed to live up to the market's sky-high expectations.

Other memory stocks were also faltering. Memory-chip maker Micron slid 3.4% and data storage company Seagate declined 3.9%.

Away from memory, AppLovin plunged 16% after the ad technology platform reported soft second-quarter results and issued disappointing guidance for the current quarter.

Meantime, Moderna rose 3.5% after the Food and Drug Administration approved the vaccine maker's mFLUSIVA, a new jab against seasonal influenza.