The Phillies also recalled third baseman Maikel Franco from Triple-A Lehigh Valley on Friday.
Adam Haseley started in right field for Harper in Philadelphia's series opener at Miami.
Harper, who flew home to Las Vegas after Wednesday's game, could miss up to three games on the paternity list.
Harper is hitting .254 with 27 homers and 92 RBIs in 125 games.
The Phillies entered Friday's game with a 66-60 record, 9 1/2 games out of first place in the NL East and two games out of the second wild card.