For experimental purposes I hopped right into juggling with no warmup. This is roughly what I noticed:
• More unstable lower body movements than normal.
• Certain muscles more tight than others.
• Soreness noticeable during play.

Granted I was sore from a workout, all of these feelings went away after a good stretch. This shows the importance of priming a muscle by stretching and strengthening it, and getting all that lactic acid out of the muscle before beginning.