The subject of service time manipulation is one we've been talking about for years. The biggest case in recent memory was Kris Bryant with the Cubs in 2015.

Remember? Bryant was sent to Triple-A Iowa to start the 2015 season, despite all the evidence in the world pointing to his MLB readiness. Not coincidentally, he was summoned after just eight games and then went on to win NL Rookie of the Year before winning the MVP next season while his team won the World Series. 

So why did Bryant need to be avoided for those eight games? The way service time is written, a "full" MLB season for a player is 172 days, where as an actual regular season is at least 178 days. As such, a player like Bryant spending fewer than 172 days in a season means he'll be under team control for seven years instead of six. 

We saw it again this season with Ronald Acuna. He wasn't brought up until April 25. He's now hitting .286/.353/.559 (142 OPS+) with 21 doubles, 21 homers and 11 steals, but hey, I'm sure those three weeks on the farm did wonders for his development. 

The latest top-notch prospects being oh-so-obviously held down with service time manipulation are Eloy Jimenez of the White Sox and Vladimir Guerrero Jr. of the Blue Jays

Jimenez, 21, is hitting .365/.406/.580 with 12 doubles and 11 home runs in 51 games for Triple-A Charlotte. He has been a monster bat at every level and is clearly ready to face MLB competition. 

Guerrero, 19, hit .402/.449/.671 in 61 games at Double-A and now has 26 games with Triple-A Buffalo, for whom he's hitting .333/.423/.548. 

Neither the White Sox nor the Blue Jays are contending, and rosters are expanding in September. And yet, we'll see neither player. The company line for the teams will continue to be some song and dance about the players needing to work on their defense or something similar, but it's obvious what is going on here. Both will make their MLB debuts next season around the middle of April, once they are cleared for a seventh year of control instead of six. 

Jimenez's agents aren't being quiet about this, via Jon Heyman of Fancred

"How can you say with a straight face this guy needs to work on anything?" wondered (Paul) Kinzer, the president of Rep1 baseball agency. "What's he need to work on?"

"Especially with elite players like Eloy and Vlad Jr., that's the nature of the business,'" Kinzer said. "It's not about the money. It's the extra year of control."

Jimenez himself recently wrote an article for The Players Tribune simply titled, "I'm Ready." 

From the players' perspective, there's very little they can do. Heyman reported Bryant's grievance against the Cubs is still pending. It was filed in 2015. If a player starts to openly complain, he paints himself as the bad guy in the public eye instead of a "grinder" who just goes about his business. 

There is value to getting a player up when he's ready instead of focusing solely on service time, too. Some players go through growing pains at the big-league level. Mike Trout hit .220/.281/.390 in 40 games in 2011 and Anthony Rizzo hit .141/.281/.242 in 49 games in the same season, just to name two examples. Experience is good. Both Guerrero and Jimenez could start adapting to MLB pitching for the next month if their teams would be willing to do the right thing. Then it would be full go for 2019. 

Instead, as noted, we're going to be waiting to see what they've got until the middle of April. 

The good news is that as the years pass by, there's more widespread focus on the development of prospects and there's even more spotlight on front offices focusing on saving money after this past offseason's free agency spree, which was a total victory for ownership and loss for the players. 

The hope here is that eventually there's enough public outcry that front offices are forced into the novel concept of a meritocracy: Just play the best players, not the ones who fit the most neatly into a long-term service time plan. 

If not, add another item to the growing list of things the MLBPA needs to address during the next CBA negotiations.