An undercurrent of frustration exists among team staffers these days as they wait for their players to return from service in the World Baseball Classic. Decisions about roster spots and starting spots must be made soon, but some candidates are playing for WBC teams, while others are competing against depleted lineups and pitching staffs in exhibition games. The most informed decisions are not possible in the current context.

"You spend all winter putting together a team," said one evaluator, "and then you don’t get to see them on the field together. It’s a little ..."

His voice trailed off without adding the last pejorative. He meant to say: frustrating or aggravating or nuts.

All teams must cope with the same challenge as they build their rosters for Opening Day of the 2017 season, and circumstances push evaluators toward the governing dynamics that mostly steer decisions this time of year: money and experience.

Some of the most notable jobs up for grabs:

Dodgers' No. 4 and No. 5 spots in rotation

Three spots are accounted for among manager Dave Roberts’ starting pitchers: Clayton Kershaw, newly paid Rich Hill and Kenta Maeda. The Dodgers seem to have as many candidates for those final two rotation spots as the University of Kentucky has assistant basketball coaches -- lots and lots. Brandon McCarthy has looked good so far this spring, overcoming the surprising case of the yips that seemed to overcome him last year. With McCarthy in Year 3 of his four-year, $48 million deal, the Dodgers will probably give him a full shot to re-establish himself, so long as he’s healthy. The same is true with Hyun-Jin Ryu, who turns 30 in a couple of weeks. He is owed $15.7 million for 2017 and 2018, after making just one appearance the past couple of years. If he’s throwing well, it makes sense for the Dodgers to capitalize on his value and hope that he can get back to being the type of pitcher he was in 2013 and '14, when he had a 3.15 ERA in 56 starts.

By employing McCarthy and Ryu in the rotation early in the season, the Dodgers could slow-play Julio Urias in April and May. The promising left-hander, so vital to the pitching staff last year, will work under an innings restriction in 2017. If the Dodgers hold him back early in the season, he will be freed to pitch more later in the season, as the inevitable injuries manifest.

Scott Kazmir has had hip trouble this spring and may start the year on the disabled list. Alex Wood is also in the mix to start, work out of the bullpen or become a trade chip. The Dodgers needed 15 pitchers to make starts last season, so they will not give away starting pitching.

Tigers’ center fielder

With less than three weeks to go until Opening Day, the competition for the spot is wide open. Sources say the Tigers don’t have a strong idea yet of who will be their center fielder, only that their general priority is defense. JaCoby Jones has had a good spring so far, but he has less than 100 games above Double-A and the Tigers might prefer to return him to the minors. Tyler Collins has been nursing a minor injury. Mikie Mahtook hasn’t hit well this spring -- he started 2-for-27 -- but has had most of his at-bats against right-handers, and the team’s evaluators want to see him with more at-bats against left-handers. Veteran Anthony Gose is viewed as a solid defender, and Alex Presley and Juan Perez are also in the mix, along with Andrew Romine, who has played well in the field.

It’s also possible that the solution will be found in the trade market: The Tigers intend to evaluate opportunities that develop as other teams make center fielders available via trade or waivers.

Matt Cain has a 5.70 ERA in 34 games over the past two seasons. Kyle Terada/USA TODAY Sports

Giants' No. 5 starter

The Giants will owe Matt Cain $28.5 million for his 2017 salary and a buyout of his 2018 option, so they are prepared to open the season with Cain filling the final spot in their rotation to see if he can provide some return for their investment. Cain has really struggled the last two seasons, with a 5.70 ERA in 34 games, and his numbers this spring are ugly: 16 hits and 12 runs in 10 1/3 innings. So Giants staffers are keeping open minds about reversing course and turning to Ty Blach, the 26-year-old lefty who won a pivotal game against the Dodgers in September. Even if Cain opens the year as the No. 5 starter, the Giants probably won’t wait long to make a change if he gets hit around in his early starts.

Yankees’ back end of rotation

Masahiro Tanaka, CC Sabathia and Michael Pineda will lead the rotation. The Yankees will need to identify the last two starters from a group that includes Adam Warren, Luis Cessa, Luis Severino, Chad Green and Bryan Mitchell. Warren and Cessa might be the front-runners halfway through camp, but the Yankees would love for two of the candidates to assert themselves and seize the opportunity. If that doesn’t happen, they could opt for experience.

A factor that gives the Yankees a lot of flexibility in choosing among the candidates: They all have options remaining to be sent to the minor leagues.

Giants' left fielder

San Francisco has some veterans who are getting evaluated for duty in left field, including Mike Morse, Justin Ruggiano, Chris Marrero, Aaron Hill and Gordon Beckham. In the end, the competition may come down to the choice that manager Bruce Bochy spoke about in the winter: left-handed hitting Jarrett Parker, who is 28 years old and had a .358 on-base percentage in 127 at-bats last year, or the powerful Mac Williamson, who is 26 years old and had six homers in 112 at-bats in 2016.

The choice might come down to the fact that Parker cannot be sent back to the minors without passing through waivers, and Williamson still can. Because teams prefer to maintain as much flexibility as possible with the maintenance of their rosters, this factor may work in favor of Parker.

Cubs' No. 5 spot in rotation

Because of how much work Jon Lester and Jake Arrieta have logged the last two years, and because John Lackey is 38 years old and has logged nearly 3,000 innings in his career, the Cubs’ front office intends to build in rest for the top of the rotation during the 2017 season. So whether the No. 5 starter turns out to be Mike Montgomery, Eddie Butler or Brett Anderson, it figures that the Cubs will find a way to keep as much experienced starting pitching in the organization as possible; all three will probably be needed to make starts during the year.

Montgomery has gotten good results so far, starting three games, walking two and striking out six in four innings. Anderson has not, with nine hits and four runs allowed in five innings. Butler’s performance has been intriguing to some evaluators in his first season out of the Rockies organization, and the Cubs have a long history of helping pitchers who have struggled elsewhere, most notably Arrieta.

Royals' second baseman

The Royals have a range of options at this spot, including Christian Colon, one of the World Series heroes in 2015; Whit Merrifield, who had 332 plate appearances in the big leagues last season; and Cheslor Cuthbert, who mostly played third base last season in the absence of Mike Moustakas.

Raul Mondesi Jr. is intriguing to the staff because he is probably the best defender of the candidates, and he possesses game-changing speed. In the minors and majors last year, he stole 33 bases in 35 attempts. The Royals aren’t sure whether the 21-year-old will be able to hit enough to win the job. So far this spring, it’s been all good -- Mondesi is hitting over .400. The Royals might prefer to keep Merrifield in more of a utility role.