Coulson knows he's in no shape to keep fighting. He braced himself against the wall, ducking, and darting his hand out quickly to swipe his card, missing on his first go, and quickly withdrawing his hand again. His second attempt landed, and door opened with a hydraulic hiss.
He hurried through, swiping his card on the other side and keying in a code to lock it. Which might hold it about a fraction of a second longer if Loki was really determined, but time was precious. He took off down the hallway, sliding his earpiece back on.
Maybe he should have held back one or two of his quips.