Short of guaranteeing a home run every time he swings, Sierra will need to show that he can run out of the box before he even leaves on a rehab stint.
He limited his workout to stretching and hitting on Wednesday, a day after the running part hadn't gone too well.
"I've had leg injuries, but this is a bit different," he said. "When I run, I just feel something grabbing in there."
Sierra, on the disabled list since July 19, estimated needing at least another week of therapy, then a week of Minor League games to tune his timing.
The one who stayed away:
Dennys Reyes broke into the Major Leagues as a 20-year-old in 1997. Yankees general manager Brian Cashman has been trying to acquire the intriguing left-hander virtually since then.
Cashman is back to trying. A day after signing a Minor League deal with the Yankees, Reyes informed the team on Wednesday that he'd had a change of heart. Reyes will remain at home in Mexico rather than report to Triple-A Columbus, as he had been expected to do on Thursday.
Reyes, still only 28, was released on July 19 by the Padres after compiling a 5.15 ERA in 36 outings, including one start.
"He's got a great arm, no question," said manager Joe Torre. "People in this organization are high on him. He's a left-hander with great stuff, and is still young."
Of his current trio of "rotation-sitters," Torre accords Al Leiter a big advantage for sticking even after the injured (Carl Pavano, Jaret Wright, possibly Kevin Brown) begin to return.
Experience is the 39-year-old Leiter's edge, despite three straight losses in which he has allowed 12 walks and 12 runs in 13 innings.
"Experience-wise, he's got the inside track, no question," said Torre, whose other choices are Shawn Chacon and Aaron Small -- who make consecutive starts on Thursday here and on Friday in Toronto.
Of Leiter's struggles, the manager said, "When I write his name in the lineup, I'm very confident when he takes the field. One change he'll have to make is going after people, not after the perfect pitch."
There is a nice decorating touch in the visitors' clubhouse at Jacobs Field -- the walls and pillars are adorned by a gallery of posters of baseball movies.
All are the original works -- "A League of Their Own," "Angels in the Outfield," "Field of Dreams" and so on -- except one. The poster for "The Natural" does not feature Robert Redford but instead has been doctored into a collage of Alex Rodriguez.
Remember Aaron Boone, and the 2003 American League Championship Series hero's bad first couple of months coming back from that blown-out knee? Boone was hitting a soft .151 as late as June 3.
Well, he's getting well. So well, in fact, that he took a monthlong .333 average into Wednesday night's game, and the Indians have restructured his contract while exercising their 2006 option on him.
Just the sight of pinstripes brings the best out of Boone: He's gone 8-for-19 in five games against the Yankees.
Chacon, who certainly did not look like a pitcher with a 2-20 record since the 2003 All-Star break in his Yankees debut, gets the ball in the finale against the Indians. Chacon held the Angels without an earned run for six innings on Saturday but will still be seeking only his third win since June 23, 2003.