Results of Wednesday's MRI will be analyzed by team doctor Neal ElAttrache, who will meet the club Thursday in New York.
Broxton said the elbow doesn't hurt while he's pitching, but that it stiffens regularly after he cools down following an appearance.
He said the stiffening was worse in Tuesday night's 4-1 loss to the Cubs after he walked consecutive batters on eight pitches, and the stiffness lingered into Wednesday, prompting him to reveal the discomfort.
"I'm fine when I'm throwing," Broxton said. "I'm fine after I get going. But it stiffens after cooling down. Warming up, it's normal. Today I came in so they could look at it and see what's going on."
Before Broxton arrived in the clubhouse Wednesday, manager Don Mattingly and pitching coach Rick Honeycutt were already watching tape of Broxton's Tuesday night outing, in which he was booed off the field after issuing back-to-back four-pitch walks with decreased velocity, when trainer Stan Conte walked into the video room.
"Stan said you don't need to look at the tape anymore," said Mattingly. "Broxt came in to complain about stuff, finally. It's honorable he's willing to pitch like this, but in the end, it doesn't do him any good and it's not fair to him and really everybody else, either. If you can't pitch the way you're capable of, it's too tough to pitch like that here."
Without using the word, Mattingly indicated he would close by "committee." Vicente Padilla was tabbed for the ninth inning Wednesday, but Mattingly won't use him on back-to-back days because of recent arm surgery. Hong-Chih Kuo inherited the closer job from Broxton last year, but he's had the yips and Mattingly said Kuo is "not throwing the way he's capable yet."
"I'm going to deal with what we have," Mattingly said. "We have [Matt] Guerrier, [Blake] Hawksworth, [Mike] MacDougal. If Kenley [Jansen] comes back, we have him."
Jansen was sent down over the weekend to make room as the club felt compelled to rush Kuo, but if Broxton is disabled, Jansen figures to return. Although his ERA was 7.43, nine of Jansen's 11 earned runs came in two awful outings. The rest of the time he was overpowering, with a total of 22 strikeouts and eight walks in 13 1/3 innings.
Mattingly said one of the immediate issues was to find an MRI tube large enough for Broxton to get his 300-pound frame into.
"I'm serious," said Mattingly.
Mattingly said Broxton told him he felt great in Spring Training, but didn't say when the discomfort started. Broxton admitted last week that his elbow was bothering him, leading to his unavailability for a game in Florida, but at the time Broxton said the discomfort was something he would normally experience during a season.
Watching his velocity drop from 96 mph on Monday to 90 mph Tuesday, however, left Mattingly and Honeycutt convinced something was physically wrong.
"That tells you something is going on," said Mattingly. "It told us what we thought."
Broxton is 7-for-8 in save opportunities, but has a 5.68 ERA with nine walks, 15 hits allowed and nine strikeouts in 12 2/3 innings.
Broxton said he couldn't rule out the possibility that the injury impacts his effectiveness, but said he isn't worried that the injury might be serious.
"If it was serious, I wouldn't be able to throw at all," he said. "There's no pain while I'm throwing."
Ken Gurnick is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.