When someone is "in the saddle," it means they are firmly in control of a situation or task. Some synonyms for this phrase include "at the helm," "in charge," "in control," "calling the shots," or simply "in command." All of these phrases imply a sense of authority and confidence in one's ability to lead or manage others. Being "in the saddle" also suggests a readiness to take action and make decisions quickly and decisively. Other related phrases that convey a similar sense of assertiveness include "on top of things," "running the show," and "in the driver's seat".