[1] Long relievers often enter in the first three innings of a game[2] when the starting pitcher cannot continue, whether due to ineffective pitching, lack of endurance, rain delays, injury, or ejection.
The quality of long relievers can vary, but when the long reliever is considered to be an ineffective former starter, he is often called the "mop up man" or "mop-up pitcher" and is often called by managers to pitch in games where there is a abundant run margin between either team which is colloquially termed pitching "mop duty".
While a long reliever is often a team's least effective pitcher[citation needed], he is still often a far better choice in an extended game than resorting to one of the team's starting pitchers (which can spread chaos throughout a pitching rotation, as everyone's future schedule gets adjusted), or even worse, resorting to a position player on the mound.
In recent years, teams began experimenting with an opener, a relief pitcher who starts a game but only pitches for at least the first inning.
In this strategy, the opener usually pitches against the opponent's best batters at the start of a game in hopes of throwing them off guard, before giving way to a long reliever who would normally be a starter in this situation.