SAN DIEGO — Ryan Zimmerman will not start Monday for the third straight game, still nursing a sore back after an awkward dive Friday night. The Nationals’ first baseman is not worried. His manager, Dave Martinez, is hopeful Zimmerman will return Tuesday. But of course they would say that. Many injuries that initially seemed small have snowballed for this team. So why is Zimmerman’s “stiff back” any different?

Well, it might not be. At this point, any skepticism about Nationals injury optimism is justified. But a few things point to Zimmerman’s trouble actually being minor.

First of all, when the Nationals activated Shawn Kelley from the 10-day disabled list Monday, they optioned outfielder Rafael Bautista to Class AAA Syracuse, which gave them a short bench. Were there concerns about Zimmerman’s ability to play soon — and even to pinch-hit Monday night — the Nationals almost certainly would have sent a pitcher out instead. They cannot afford to carry two healthy position players and a catcher on their bench.

“After talking to him last night, he said he felt pretty good, so we thought we could use another arm in the bullpen,” Martinez said.

Secondly, Zimmerman himself said “today was the best he felt,” and called that “good news,” saying he just wanted to test things out today. He went through throwing drills in the batting cage. He hit on the field with his teammates, with Martinez and hitting coach Kevin Long watching from a few feet away. Zimmerman originally estimated he could be back in the lineup Monday. Martinez saw no need to rush.

“I just wanted to make sure that he’s feeling really good. He’s going to go out and do all the baseball activities, and we’ll go from there,” Martinez said. “I’m glad he’s feeling better. It’s one of those things where you just don’t know. He hit the ground pretty hard, and his back was stiff, everything was stiff. To give him another day is nice.”

The Nationals face Padres right-hander Tyson Ross Monday night, but then face two lefties Tuesday and Wednesday. With Matt Adams available and dominating right-handed pitching, Martinez said the Nationals didn’t need to rush Zimmerman, whose importance grows against those lefties in the rest of the series.

The question, of course, will be whether Zimmerman is actually available.

WASHINGTON NATIONALS (18-17)

Bryce Harper RF

Trea Turner SS

Anthony Rendon 3B

Matt Adams 1B

Howie Kendrick LF

Matt Wieters C

Michael A. Taylor CF

Stephen Strasburg P

Wilmer Difo 2B

SAN DIEGO PADRES (13-22)

Travis Jankowski RF

Eric Hosmer 1B

Franchy Cordero LF

Raffy Lopez C

Chase Headley 3B

Jose Pirela 2B

Freddy Galvis SS

Manuel Margot CF

Tyson Ross P