Folks either demand an explanation or make up one. One theory that makes Jimenez chuckle is that he's somehow too nice.
"Last year, probably nobody would say that when I get into the game," Jimenez said, not with defensiveness but with a bemused smile. "But that's the way it is. Every time you're not performing the way you're supposed to, people are going to say everything. They're going to be thinking a lot of things.
"The only thing I can do is get ready to win this game, try to help my team out. I'm going to be hearing things. I'm going to be reading things. I'm not going to let any of those things get into my mind, because I know how it is."
But guesses come in the absence of a solid explanation.
The start to Jimenez's season was startling, but it made sense when examining his little, nagging injuries. A cut on the cuticle of his right thumb sustained during Spring Training flared up just before Opening Day and cost him two regular-season starts. Jimenez also worked through right hip flexor and right groin injuries during the spring.
However, it's difficult to explain Jimenez's erratic performance in his past five starts.
Three of them -- two against the Giants, on May 6 and May 17, and against the Brewers on May 22 -- suggested that Jimenez's form was returning. He held opponents to 12 hits and struck out 18 over 21 innings in those games. The Rockies won one of them. In the other two he was merely another unintended victim of the team's offensive struggles.
But in the other two, against the Mets on May 12 and against the Cardinals on Friday night, he gave up 11 runs and 15 hits in 9 2/3 innings.
The start against the Cardinals effectively threw his season into the mystery category. Jimenez was coming off a two-hit complete game in a heartbreaking 3-1 loss at Milwaukee, but gave up 12 hits and six runs in six innings of the 10-3 loss to the Cardinals. Hitter after hitter sent two-strike fastballs the other way for line-drive hits.
Is Jimenez getting right, or is everything all wrong?
"Honestly, I think he's the one you're going to have to ask," Rockies catcher Chris Iannetta said. "He knows what he's feeling mentally, physically, competitively. He can have a better assessment. I'm back there and I see what I see. I see a guy that's different from what he's been in the past. Hopefully, he knows what's going on and can get back to where he needs to be and wants to be."
Shortstop Troy Tulowitzki said, "We keep on looking at it like right now it's still early in the season and when we need him most is going to be late in the season. But last year at this time I don't know what his record was, but now he hasn't won a game yet. So there is concern. But there are signs that it's coming back."
Beyond his warm smile, Jimenez's calling card while winning 14 of his first 16 starts last year, en route to a 19-8 record and 2.88 ERA, was his sizzling fastball.
According to FanGraphs, a Web site that collects raw PitchFx data and analyzes it, in 2009 and 2010, Jimenez's average fastball velocity for each start rarely was below 95 mph. This year, that average has been at or below 95 in each start. The 94.0 average for the season is 1.7 mph below his career average.
In addition, according to FanGraphs, Jimenez's hard slider has seen a drop from 86.4 mph last season to 82.6 this year.
Rockies pitching coach Bob Apodaca said the radar reading is just part of the issue.
Whether he's dominating or struggling, Jimenez's pitching mechanics are unorthodox because he extends his arm downward more than most pitchers before whipping it forward. For it to work, however, Jimenez needs his body to be in a position to generate power.
If his arm and body positioning aren't in sync, Jimenez has to lift his body upward on his stride to the plate. That movement costs him power and leverage from his long-limbed, 6-foot-4 frame.
"That's like filling a balloon with air but having a little pin prick and letting the air slowly seep out," Apodaca said. "All that potential power is going slowly and then when you unleash the balloon, there's not that power.
"By holding onto that balloon with no pin prick, all of a sudden ... phew. All that power is there for you."
It's not just velocity that he's lost. Against the Cardinals, Jimenez lacked the downward bite on his fastball. The result: pitches just high enough for hitters to handle.
Jimenez insists he is healthy and the velocity will come. He takes heart in the belief that mechanics are at the root of the problem. His delivery was even funkier when he was in the low Minors. Shoulder issues led to surgery and forced him to make modifications. He also had to clean up his mechanics after struggling early in 2008, his first full Major League season.
Jimenez admitted that making the little tweaks Apodaca has suggested is difficult when you go from a bullpen session to facing hitters wanting to do damage and game situations that call for execution. But he said it's not like the situation is new to him.
"Every now and then I'm going to lose my mechanics," Jimenez said. "It's not easy mechanics to do what I do out there, especially when I'm trying to throw hard and trying to execute pitches at the same time. I've dealt with that before. That's why I think this is not bothering me.
"When I want to let it go, I let it go. I'm trying to find the point that I will be consistent. I want to do things exactly how I want it."