But things have changed for the Nelson. On Wednesday night, the right-hander turned in 1 2/3 innings of scoreless relief to give him five shutout innings this season, making him the only Rays pitcher who has yet to give up a run.
When asked about the reversal of fortunes, Nelson chuckled: "You mean from when I was the lone bomb giver-upper during Spring Training?"
Nelson conceded he's feeling a lot better on the mound, but not all the way to where he wants to be yet.
"[I'm] still dealing with a little mechanical thing that I talked to [pitching coach Jim Hickey] and [assistant pitching coach] Brian Anderson about," Nelson said. "I think there's definitely room for improvement. We've been working on it today, and I think something clicked."
Nelson believes a lot of the difference has been in his ability to establish his fastball.
"If I think they're sitting changeup, then I usually stay with fastball, and if I think they're sitting fastball, I throw a changeup," Nelson said. "It's no secret. It's just executing pitches."
While performing well surely will pump up Nelson's level of confidence, he insists he remains confident even when he's struggling.
"And I'm confident right now that I'm executing my pitches," Nelson said. "My velocity is not where I want it to be. I attribute most of that to mostly mechanical stuff."
In addition to feeling confident, Nelson feels comfortable throwing at Tropicana Field.
"I liked throwing here in the past," the former Marlins righty said. "I threw here two times last year -- those were the first times. It's a great mound. It's got good slope. And home plate is very close to the backstop, which always makes you feel like you're right on top of the hitter. Fenway's the same way.
"The perception can affect everybody differently. But when the backstop is close, I feel like I'm right on top of the hitter. My weak old fastball feels like I'm getting it on them even though I'm probably not."
Rays manager Joe Maddon noted how effective Nelson is against left-handed hitters.
"And that's what makes him really valuable," Maddon said. "He does well against righties, but he can do very well against the lefties, too.
"The big thing is just to get his feet on the ground here with the Rays. I think he is getting more comfortable."
A level of comfort that is reflected in results.