WEST PALM BEACH, Fla. — The Washington Nationals had a pitching plan, and soon they had another one because the World Series and weather are out to make this complicated. But even with all that happened this weekend — a rainout Saturday, then a split-squad scrimmage Sunday — there is an unchanged variable: The Nationals will ease relievers Sean Doolittle and Daniel Hudson into action. And this, they believe, is critical.

It’s not that Hudson and Doolittle aren’t healthy. They actually feel good, at least for spring, and have thrown their share of bullpen and side sessions. But this being the year after a deep playoff run and the back half of the relievers’ injury-filled careers, the Nationals aren’t chancing it. How their bodies hold up could very well decide how the bullpen fares this season.

The Nationals added Will Harris, hope Tanner Rainey and Wander Suero make strides, and expect bounce-back years from Hunter Strickland and Roenis Elías. Yet the ninth belongs to some combination of Hudson and Doolittle, two veterans who battled right knee pain throughout 2019. For Doolittle, 33, it led to arm fatigue and a late-season trip to the injured list. For Hudson, who turns 33 in early March, it made for an uncomfortable title run.

So the plan, now and moving forward, is to keep their knees from throbbing and keep their arms fresh.

“When you get knee pain, the muscles on top of your knee shut down,” Doolittle said. “The glute shuts down. Your body is trying to protect it by saying: ‘Don’t use it. We’re not going to let you use it.’ It can lead to bad habits, and that’s a slippery slope.”

Hudson pitched with a strained medial collateral ligament in his right knee in August, September and October. He suffered the injury at the end of the summer, made nine appearances in September — including saving both legs of a doubleheader — and threw 9⅔ innings in the postseason. He couldn’t receive cortisone because team doctors were worried about further damaging the MCL. By the fall, before he threw the final pitch of the World Series, he was running on nothing but adrenaline and anti-inflammatory pills.

Some days Hudson would start warming up in the outfield and consider shutting down. The pain became close to unbearable more than once, but he pushed to the end. The Nationals trusted six total pitchers for the entire playoffs. Hudson was one of them. But he knew, once winter arrived, that he needed to reset. He took November off. He went to physical therapy three times a week near his offseason home in Phoenix.

He then signed with the Nationals in mid-January, on a two-year deal worth $11 million. There was hesitancy because of Hudson’s injury history, including back-to-back Tommy John surgeries that forced him to miss most of three years. But his arm recovered well, his knee did, too, and his mechanics hardly slipped.

“There were times when I started to feel my arm overcompensating for my knee being sore since it was my back leg and I was trying to generate force and velocity,” Hudson said. “But it never got to the point where my elbow or shoulder was in jeopardy. If it did, I wouldn’t have been pitching. I was able to make it through.”

Doolittle’s knee issues go back a decade, to when he underwent surgeries in 2009 and 2010. The first procedure reattached a patellar tendon that had badly frayed. The second was a debridement, with doctors cutting a sliver off a tendon and shaving down his kneecap. They derailed his career as an outfielder and ultimately led him to pitch for the Oakland Athletics; he was traded to Washington in 2017.

That snowball effect is the good part. The bad side is the lingering tendinitis that flared up this past spring. That’s what led Doolittle to the IL in mid-August, even if it seemed like a bout with arm fatigue. He had to shoulder a heavy workload in the spring and summer — with 39 first-half appearances — and has not pitched a full season without injury since 2013. Then his knee pain created bad habits in his delivery, which created arm soreness, which created the need to sit him down for two weeks during a pennant race.

But in that stretch, Doolittle developed routines he will carry into the coming year. He focused less on heavy lifting. He did more agility work and retrained his body to complete movement patterns that had become strenuous. He used a muscle-stimulation machine twice a day — once when he got to the park and again in the early innings of each game — to activate his knee by fighting through contractions.

The result was a 1.96 ERA in 18⅓ innings across September and October. Doolittle then rented the same machine this winter and maintained the same upkeep.

“I don’t think I’ll ever be out of the woods with my knee, but I feel like we’ve learned a lot with how I can manage it,” Doolittle said. “I don’t think there will ever be a day where I can just show up at the field without doing the activation and my maintenance program.”

The Nationals needed 14 pitchers to take the mound Sunday. Eight faced the Houston Astros in a 2-1 win in West Palm Beach. The rest appeared in a 5-2 loss to the Miami Marlins in Jupiter. But Doolittle and Hudson threw in the morning, on the back fields of Washington’s facility, against batters in a controlled setting.

It was their latest round of baby steps and will lead right into another.