Manny Parra of the Brewers pitched the last 6 1/3 innings of his team's 8-5 loss to the Mets in Milwaukee. No NL pitcher had thrown at least six innings of relief since Carlos Villanueva of the Brewers did back on September 15, 2006 in Washington.
Long relief stretches are more common in the AL where the DH rule allows a manager to avoid to deal with possible pinch hit situations. Five AL pitchers had already pitched at least six innings in relief this year.
Parra also batted twice as a reliever, but that is not that unusual. Bob Shaw of the White Sox batted SIX times in a game on April 22, 1959 while pitching in relief of starter Early Wynn.