"I think he's close," Murphy said of the All-Star outfielder.
Upton made a nice running snag toward the left-field line of a ball hit by Scooter Gennett. His momentum carried him toward the seats, where he braced himself against the rails.
Murphy said Upton's main issue now is trying to throw the ball.
"I think the throwing's more of an issue than the swinging right now. He can't play defense," Murphy said.
There's about three feet of padding that goes up from the ground down the third-base line, but nothing above that other than the rails that separate the fans from the field. That's where he hurt his thumb.
"There isn't a better spot for padding [than] there. That railing is pretty inconvenient," Upton said after Monday's game.
Upton, who is hitting .247 with 18 home runs and 57 RBIs, was replaced in left field Tuesday by Will Venable with Melvin Upton Jr. getting the start in center field.
• Pitcher Ian Kennedy was reinstated from the paternity list before Tuesday's game. He'll start Wednesday against the Brewers. Kennedy flew home to California from Miami on Saturday, one day after his wife, Allison, gave birth to the couple's fourth daughter, Evelyn. He got three days with his family, including their other three daughters.
"It was great. It was a lot of fun," Kennedy said. "It was nice to get everyone set-up at home and get everyone unpacked."
Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.