As ish, a commenter pointed out, Dave O'Brien was barely there for the 4/1 game in Oakland, which I heard most of. Joe C. acknowledged early that Dave had an ESPN committment in NY on April 2 (a night game).
Accordingly, Joe C called the first inning and, unconventionally, Dave called inning 2, 3 and 4. Joe was all alone for the balance of the game. Probably Dave had to catch the red eye from SFO-JFK, so he beat feet. It was a little weird. Therefore, Dave gets credit for a half game called in the running total to the right.
In today's game, Joe is all alone, with the local scribes filling in some dead space: Sean McAdam and Gordon Edes. Gordon observed that "I am sure from time to time, you have had to do a solo in your career"
Joe responded with deafening silence. He didn't seem too happy about it.
I can only remember one similar situation in all the years I have been listening. It was a Sunday night game, the last game before the All Star Break when Joe was announcing with the late Bob Starr. Starr was scheduled to return home to California for the break. When the game went into extra innings, Bob left to catch his flight, and Joe soloed the rest of the way.