CHICAGO -- The Cubs have been navigating through a rash of health setbacks over the past month. Another setback arrived Thursday with veteran right fielder Jason Heyward landing on the injured list.

Prior to the finale of a four-game set with the Nationals, the Cubs placed Heyward on the 10-day IL with a left hamstring strain and recalled outfielder Nick Martini from Triple-A Iowa. At the moment, Chicago has eight players on the IL.

There are also five players on the Cubs' active roster who had non-COVID-related stints on the IL already this season. And a day after Heyward left with his hamstring issue, Cubs lefty Justin Steele exited Thursday's game with right hamstring tightness in the top of the seventh against Washington.

"What we've been dealing with from an injury standpoint I don't think is uncommon in baseball right now," Cubs president of baseball operations Jed Hoyer said on Thursday morning. "You look around the league and there's a lot of injuries.

"We're going to sit down with [the high performance staff], sit down with the coaching staff and talk about why on our end. I think other teams are going to do the same thing. I think we all had a concern that there might be more injuries this year.

"Figuring out exactly why it's happening early in the season, I think, is a real question that we have not answered yet obviously. There's a lot of variables there. But, depth is going to be tested, I think, for everybody."

Cubs manager David Ross said the hope with Heyward is that his injury is "on the milder side" and will not result in a lengthy absence. For Thursday's game, Martini got the start in right field, while Kris Bryant was out of the lineup for a scheduled day off.

Bryant has been critical in helping Ross maneuver around setbacks in the outfield. Joc Pederson, Ian Happ, Jake Marisnick, Nico Hoerner and Heyward have all dealt with injuries at various points, while Bryant has moved between all three outfield spots (plus first base at times) to stretch the roster's depth.

"His versatility has been amazing," Hoyer said of Bryant. "I think you think about versatility normally as kind of the utility infielder, the little guy that can play short, second and third. His ability at his size and with his offensive profile to be able to move around, really, sometimes I think we don't give him enough credit."

Hoyer 'disappointed' in Cubs' vaccination progress
Prior to this season, MLB informed teams that clubs who achieve 85 percent of Tier 1 personnel getting vaccinated against COVID-19 could have restrictions relaxed. The Cubs remain below that level, which has been discouraging to Hoyer.

"It's disappointing, yeah," Hoyer said Thursday. "It's disappointing to not be at 85 percent as a team. I think we've worked hard to get as many people vaccinated as possible. We've worked hard to try to convince or educate the people that have been reluctant. I think we're at a place right now, candidly, where I'm not going to give up hope that we can get there, but my level of optimism is waning."

Hoyer added that it is "irrefutable" that reaching 85 percent comes with competitive advantages, especially in terms of contact-tracing procedures in the event of any positive tests.

"We're missing that," Hoyer said. "It's a part of the job that I never quite imagined, that you'd be involved in that kind of education, that kind of convincing. But we haven't been able to get there. I'm not sure we're going to be able to."

Worth noting
• Entering Thursday, second baseman Nico Hoerner was batting .345 with a 139 wRC+ in 16 games since being called up from the Minor Leagues. He also had four Defensive Runs Saved in 81 2/3 innings at second.

"He's been outstanding," Hoyer said. "As far as the decision in Spring Training, to be candid, I don't have any regret over [starting Hoerner in the Minors]. I think David Bote is a really good player. I think giving him a chance to really establish himself and to have that role was the right decision in that moment. We couldn't believe in Nico more."

• First baseman Anthony Rizzo returned to the starting lineup for Thursday's game, following a day off to rest a back issue that flared up during Tuesday's game against Washington.

Quotable
"I'm glad he got the base up. Definitely, if he wouldn't have been able to get the base out of the ground, that would've been a little embarrassing. I was thinking, ‘Man, I don't know that I would've been able to get the base out.'" -- Ross, on Nationals manager Dave Martinez removing first base and tossing it during an animated ejection on Wednesday night