From 1988: TV veteran Richard A. Colla discusses his life in SF TV with STARLOG MAGAZINE... including his stint directing (most of) the BATTLESTAR GALACTICA pilot episode (and faux feature film) SAGA OF A STAR WORLD.
A quick re-read of the interview is interesting.... He doesn't seem to mention that he had an almighty bust-up with Glen Larson during the shooting of Saga and was fired from the project before principal photography was completed. According to other accounts, there was only four days left on the schedule when he was replaced.
His uncredited successor was another small-screen trooper Alan J. Levi. Larson had already booked him to deliver the next story to shoot, the two-part Hoth alike (but shot more than six months before filming started on EMPIRE) GUN ON ICE PLANET ZERO. Levi was dragged in early to pick up where Colla was forced to leave off.
The reason for the sacking? Colla claims Larson was interferring too much with the filming and a succession of minor disagreements eventually escalated into his dismissal. I'm sure Iove seen Larson claim he has let go because the shoot was too far behind schedule and costing too much. I suspect both are probably close to the truth. The sheer amount of shot-but-never-used footage for the opener (see the DVD and BR releases) is a sure sign that, behnd-the-scenes, the decision-making process was a little murkey.
Trivia of the day: Directing TV pilots can be a lucrative business. If the show sells and goes to series, the original director continues to recieve a per-episode payment for establishing the initial look-and-feel of the show (including key elements like casting, costume etc). So, even if the director is never invited back (or doesn't want to go back), they'll continue to profit from the success.