I’ve tried Googling this, but I cannot seem to find an answer. I keep getting the history of the relief pitcher.
What is the earliest point in a game in which a relieving pitcher has been brought in?
Here’s a case of a pitcher leaving the game after being hit in the hand by a line drive from the first batter.
Is that what you’re looking for or are you looking for a non-injury reason for the relief pitcher?
In 1917, when he was still a pitcher for the Red Sox, Babe Ruth walked the Senators’ lead-off batter. He then got into an argument with the umpire over the call, got tossed out of the game, and punched the umpire.
A relief pitcher, Ernie Shore, came in. The man who had been walked by Ruth was thrown out attempting to steal second base, and Shore then retired the next 26 consecutive batters.
https://baseballhall.org/discover/babe-ruth-made-history-with-help-from-ernie-shore
Just to add: according to the article linked below, Mr. Ruth walked the lead-off batter on four straight pitches.
Ideally, due to non-injury. But this does answer the question as phrased. 
I love then “and then punched the umpire.” You know … as you do.
Allow me to restate the question for some additional clarity of what I’m looking for. The replies so far have been great, and I’d love more of those too.
What is the earliest point in a game when a coach chose to replace a pitcher? I.e., was not forced to for any reason.
Pitchers too numerous to list have failed to retire a single batter and been removed with zero outs in the first inning.
Going back to injuries, there have been cases where pitchers injured themselves during the pregame warmup and were removed before throwing a single pitch. In fact this once happened at an MLB game that I attended. The removed pitcher is still credited with a game played and zero innings pitched because his name was on the lineup card handed to the umpires before the game.
Clayton Kershaw was pulled in the first inning of a playoff game, having given up 6 runs and only recording one out.
Huh. That surprises me. I would have thought it would be very rare. Probably why searching for it wasn’t coming up with anything. Thanks!
It’s probably not possible to tell the actual answer to your question, because fans and reporters may not always know when a manager is removing his pitcher because of a possible injury, or when the manager has just seen enough, thankyouverymuch.
If you’re looking at batters faced rather than outs recorded:
On July 19, 1974, with me in the park, the Twins manager pulled Vic Albury after three batters (homer, single, walk if you’re scoring at home). Thirteen-year-old me found this so bizarre he wrote a note to that effect on his scorecard (“three batters? really??”). But for all I know Albury was hurt and I just never found out. Jerry Reuss faced four batters on 9-24-77…again, I don’t know whether this was a “forced” exit or not, and it’s possible no one knows.
Case in point: Mark Hutton of the Marlins on 8-20-96. He pitched a no-hitter! Well, no, he didn’t. But he deidn’t give up a hit either. he walked the first three batters he faced, then hit Sammy Sosa with a pitch, then walked the fifth batter, and Hutton was suttonly but not surprisingly out of the game.
Sometimes a guy just doesn’t have it.
That’s fair. Apparently, a pitcher being pulled in the first inning is not as rare as I would have expected. I appreciate your additions.
Babe Ruth once walk the first batter and got thown out arguing it.
The reliever got a double play and went on record what was considered at the time a no hitter.
Not a double play, but a caught stealing, and see post three
Yep, I was going from memory when I moved and tagged the thread. It is one of my favorite Baseball stories. Especially as it involved Babe Ruth.
Happened at a game I was at in 1993. The starter gave up a single, four walks, and a grand slam; tore a ligament, and was replaced by a reliever without getting an out.
The pitcher in question was Nolan Ryan. He was already planning to retire at the end of the year. The torn ligament mean he missed his last two planned starts. His last game was supposed to be at home; I’m sure there was a lot of disappointment among the Rangers that he didn’t get the chance.