There’s an old saying in baseball that “momentum is only as good as your next day’s starter.”

For a few weeks there, it didn’t matter who the Cubs’ starter was. Or who the opponent’s starting pitcher was. Or how many names were on the injured list.

The Cubs wrapped up a historically good month in May and began June on that same heater, sweeping the San Diego Padres at Wrigley Field. The Cubs have fallen back to Earth a bit on the West Coast on the current road trip, including a 9-4 loss in San Diego Monday.

The Padres entered 2021 fresh off an aggressive offseason and clear World Series expectations. One such move over the winter was the trade with the Cubs to acquire Yu Darvish, who is slated to start the finale of this series Wednesday afternoon in San Diego.

That deal may have changed the external expectations for the Cubs but internally, they still felt like they belonged with the best teams in the National League. A hot stretch helped prove that belief but this is a Cubs team stocked with veterans who have long track records in October and a manager at the helm who knows how important it is to take things one day at a time.

At the outset of the West Coast road trip, David Ross was asked about the external expectations for his team and brushed aside any notion that things have changed after the Cubs’ 21-8 stretch.

“We’ve got a long ways to go,” Ross said Thursday. “We’re two months in. But I don’t know that there’s raised expectations. The narrative coming in was one thing and we’ve played good — we had a good month. I’m super excited about that. We still have a lot of challenges ahead of us and a long season and a long way to go.

“It’s nice to continue to prove to yourself that what you believe is true, that we have a good team that’s capable of winning baseball games and beating anybody. But we have to go out and prove it nightly. That doesn’t change.”

San Francisco was a reminder of how difficult that can be at times, especially against contending teams.

Momentum is intangible and largely impossible to create and maintain since there are so many external factors that come into play — umpire calls, wind, weather, fans, the way a ball bounces, injuries, how the opponent is playing on that particular day, etc.

Ross simply wants the Cubs to focus on bringing the same mindset to the field every day and believes strongly that if this team can do that, they’ll be where they want to be at the end of the season.

“We just went on a really nice run at home — we felt like the momentum, everything was going our way,” Ross said. “There’s times in a season where that plays a factor, too. Our goal here is to control what we can in our daily process and coming out and preparing to win and going out there and doing our best on that day and giving what we’ve got that day to try and win that ballgame.”

Marathon mindset

Part of that daily process has been understanding and digesting that this is a normal, 162-game season.

Monday marks the Cubs’ 60th game of the year, which last season would have served as the final game of the schedule before the postseason.

The hair-on-fire intensity of last year’s regular season is no longer at play and that took some getting used to for the Cubs this spring.

“I think [the players] were still in that mindset of ‘we gotta prove it right now’ and they wanted to be better, especially offensively,” Ross said. “We all knew what talent we had in the locker room from experiences but we hadn’t seen it in a while. If you know what kind of talent you bring to the table but you’re not able to show those or you’re not able to show up on a consistent basis when you get back to being in front of people and playing on TV and wanting to perform, you put a lot of pressure on yourself.

“I think these guys were definitely still in that spring mode. And once they settled into the season, you just started to see the versions of them that we know are there. I still think there’s better versions of a lot of guys that we haven’t even seen yet that are coming as well. That’s the exciting part.”

The Cubs feel like they’ve been in a good place with that concept for a while now. Ever since the Braves series at Wrigley Field in mid-April, this team has allowed that daily pressure from last season to dissipate.

Injury updates

The Cubs activated outfielder Jake Marisnick off the IL Monday and optioned pitcher Kohl Stewart to Triple-A Iowa. Marisnick had been on the shelf for nearly a month after suffering a hamstring strain on May 9.

Joc Pederson (back) missed Sunday’s game and wasn’t in the lineup again Monday but was planning to go through a full pregame routine.

Javy Báez left Sunday’s contest with a thumb contusion suffered on a swing and is considered day-to-day. Sergio Alcántara got the start in his place at shortstop Monday.

“We want to make sure he’s in a good place and not push anything that may be long-term and that’s why he’s out of the lineup today,” Ross said. “But we’ll try to assess that daily of how he’s feeling and making sure that he’s 100% or being able to give us an at-bat off the bench for a couple days. We do have an off-day coming up so it would be dumb to push something too soon.”

Trevor Williams (appendectomy) is playing light catch and doing arm maintenance but will still be on the shelf for a little while longer.

Justin Steele (hamstring) threw a bullpen Sunday and will likely throw another bullpen before heading out on a rehab assignment. The Cubs hope to have their rookie southpaw back in the fold soon.