Gio Gonzalez is the Nationals’ only left-handed starter and has been a constant for them for five years, but he is not a lock to be in the rotation in 2017. (Jonathan Newton/The Washington Post)

Two years ago, the Washington Nationals ambled into the offseason woozy from a disappointing National League Division Series loss with a few obvious weaknesses. Starting pitching wasn’t one of them. They had Stephen Strasburg, Gio Gonzalez, Tanner Roark, Doug Fister and Jordan Zimmermann together for at least one more season and a few promising prospects in the minors. They signed Max Scherzer to a seven-year, $210 contract anyway.

Two years later, the Nationals are coming off another division series defeat seeking to surround a strong nucleus with the right complementary pieces so they can take the next step. They need to address the back end of their bullpen. They would prefer not to have Jose Lobaton and Pedro Severino as their catchers. They must figure out where Trea Turner will play in 2017.

They have needs, but starting pitching isn’t one of them. Led by Scherzer, the Nationals might have the deepest group of major league-ready starters in baseball. But that doesn’t preclude them from doubling down on their strength again.

“We never stop looking for starting pitching,” General Manager Mike Rizzo said at the GM meetings outside Phoenix last week.

This free agent class doesn’t feature a starting pitcher anywhere near Scherzer’s caliber — Strasburg’s contract extension in May leaves Rich Hill, who will be 37 next season, as the best available starter — but there’s always the trade market, and the Nationals have the assets to go either way: They could add another starter, or they could trade from their surplus to address other departments. Or they could do both. Those prospects might hinge on Gonzalez.

As expected, the Nationals began their offseason transactions by exercising Gonzalez’s option for next season. His ERA escalated nearly a full run, and his velocity dropped in 2016, but paying $12 million for a 31-year-old left-hander with Gonzalez’s track record is a sound investment in today’s market.

Since he joined the Nationals in 2012, Gonzalez ranks ninth in innings pitched and eighth in FanGraphs’ Wins Above Replacement among left-handed starting pitchers. He’s sixth in strikeouts per nine innings and seventh in total strikeouts — behind Clayton Kershaw, Chris Sale, Madison Bumgarner, David Price, Cole Hamels and Jon Lester. He has been on the disabled list just once — in 2014 with shoulder inflammation — has reached double digits in wins in all five seasons in Washington and has made at least 31 starts in four of them.

That consistency makes Gonzalez one of the better end-of-the-rotation starters in baseball. It also could render him a valuable trade chip to address other roster needs, but Rizzo indicated he doesn’t plan on dealing Gonzalez, whose contract has a vesting $12 million option for 2018 if he logs 180 innings next season.

“I would not describe him as expendable at all,” Rizzo said. “To me, he’s a reliable starter that takes the mound every five days, and those guys are worth their weight in gold.”

Yet Rizzo implied Gonzalez’s spot in the rotation isn’t a lock and there will be competition for the final two spots. The other options include Joe Ross, Reynaldo Lopez, Lucas Giolito, A.J. Cole and Austin Voth, who posted a 3.15 ERA with Class AAA Syracuse in 2016 but has yet to pitch in the majors. Gonzalez is the oldest of the bunch by seven years and the only left-hander, but Rizzo said handedness is secondary in constructing a rotation.

“We feel fortunate in the depth we have in pitching at the big league level and prospect wise,” Rizzo said. “I know that every team we talk to would like to be in the same position we are as far as starting pitching goes.”

Lopez soared from Class AA Harrisburg past the more heralded Giolito on the organizational depth chart by the end of 2016 to make the playoff roster as a reliever. Rizzo acknowledged the 22-year-old Lopez’s high-90s fastball and knee-buckling curveball are suitable out of his bullpen, but the Nationals are “going to give him every opportunity to be a starter.” Giolito’s role isn’t disputed, but after registering a 6.75 ERA in 211/3 big league innings, the top prospect probably will start 2017 in the minors.

“We learned that he failed for the first time in his life,” Rizzo said. “He pulled himself up, had a good, positive attitude at the end and saw that they don’t hand things to you in the big leagues. They don’t care about your prospect status. You’ve got to execute to get guys out at the big league level. I think that the failure he felt for the first time I think makes him better, stronger and more prepared to compete next year.”

As the Nationals stand, the competition to fill out the rotation will be crowded again.

“That’s the currency of this game — starting pitching,” Rizzo said. “The more controllable good starting pitchers you can find is what it’s all about. We’re always on the hunt for it.”