If starters and closers are the Supermen on a pitching staff, getting all the notice, then long and middle relievers often play the Clark Kents, keeping low profiles.
Alan Mills has been the Orioles' Clark Kent of the first half of the season, leading the major leagues in average innings per appearance and the American League in relief victories.
He has the stuff to be a closer or a starter, but, like Superman's alter ego, Mills prefers not to make waves about his skills or his aspirations.
"It's a long season, and I don't want to talk about myself," Mills said. "You try not to get too high or too low."
"We don't let him say anything," manager Johnny Oates said, jokingly.
That's fine, because the numbers Mills has posted to date speak loudly enough. Mills, 25, has a 7-1 record and a 1.22 ERA, the lowest on the Oriole staff. He also has the second-best winning percentage in the majors, behind the Toronto Blue Jays' Juan Guzman.
For the season, batters are hitting .186 against him, with right-handers hitting .181, and left-handers .191.
At home, Mills has surrendered three earned runs and 18 hits in 28 2/3 innings for an 0.94 ERA and a 5-0 record.
Mills has been especially spectacular in July, going 2-0 with his first career save. He has not given up a run in five appearances this month over 10 1/3 innings.
"He's got some aptitude," pitching coach Dick Bosman said.
That Mills has big-league stuff is evident, but his success is something of a shock, even to the Orioles staff.
"Sure it's a surprise. Here's a guy who hadn't done anything at this level," Oates said. "I guarantee that if it wasn't a surprise, we wouldn't have him."
The Orioles obtained Mills from the New York Yankees for two minor-leaguers on Feb. 29 in a deal that didn't appear to be of major consequence.
After all, Mills hadn't done anything of consequence in two major-league call-ups with the Yankees, though he had become the first New York prospect to leap from Single-A to the big leagues, when he joined the parent club in 1990, after a 6-1 mark with an 0.91 ERA in 1989 with the Prince William Yankees.
"The experience in New York was not a good one for him, and he needed to develop some confidence," Bosman said.
Mills had a decent spring training this year, but was sent to the Triple-A Rochester Red Wings.
When middle reliever Mark Williamson developed elbow inflammation and was placed on the disabled list, Mills was called up April 17 and has been sensational.
Consider the past eight days. Last Saturday, he worked four scoreless innings in the Orioles' 3-2 loss to the Minnesota Twins in 15 innings. Mills was in position to get the win, but closer Gregg Olson surrendered two runs in the bottom of the 15th.
Monday night, Mills pitched two more scoreless innings and got the victory in the 4-3 win over the Chicago White Sox in 14 innings. On Wednesday, Mills pitched another scoreless inning in relief of Mike Mussina for the win, and he saved Arthur Rhodes' first major-league victory Thursday night.
By Oates and Bosman's reckoning, Mills is capable of working long, short, or even starting.
Given the Orioles' problems with the fourth and fifth spots in the rotation, Mills would seem as good a candidate as any to become a starter.
But Mills will remain in the bullpen for the time, which suits him fine.
"I don't even want to think about that," Mills said.
As you may have gathered, Alan Mills is not the talkative type, especially when the subject is Alan Mills.
When his mother sent him a hometown Lakeland, Fla., newspaper story about him, Mills said he wouldn't read it. Likewise, he won't read local papers and gets his baseball news from USA Today. That way, he says, he won't read about himself and get a swelled head.
Even with his success, he has not bought a house nor rented an apartment, but instead is living in a hotel.
But that may have more to do with convenience than caution because he does not have to put down a security deposit and he gets an indoor pool and sauna.