VIEIRA, Fla. -- In the six days since the St. Louis Cardinals announced they would be without All-Star shortstop Jhonny Peralta for the early months of the season because of a thumb injury, prospect Aledmys Diaz has started four games at shortstop.

It certainly appears as if the Cardinals are giving the 25-year old, who played five seasons of Cuban professional baseball, the first crack at replacing Peralta. But manager Mike Matheny bristled when he was asked if Diaz is the frontrunner due to his superior defense.

Cardinals prospect Aledmys Diaz has gotten four spring starts at shortstop since Jhonny Peralta's thumb injury. AP Photo/Jeff Roberson

“Is that your evaluation? I don’t want it to come across like I said that,” Matheny said. “My evaluation is we haven’t had enough of a chance to make a statement like that.”

The Cardinals haven’t ruled out making a trade for a more established shortstop, but they also haven’t ruled out letting Diaz make his major-league debut on Opening Day, April 3, in Pittsburgh. They also could mix and match with Jedd Gyorko, who would presumably provide more power.

The team’s top infield instructor, Jose Oquendo, said he has seen big strides in Diaz’s defense in the past 12 months. Oquendo thinks Diaz’s right arm was sore all of 2014 because of all the throws he made while trying out for major-league teams at his showcase.

“I think he can help us right now. It’s just a matter if they feel he has enough games yet, because he’s been hurt in the past,” Oquendo said. “Last year is the first year he’s really been healthy. If he keeps doing what he’s doing right now, it feels like he’s going to be OK.”

Diaz has been sporadic with his hitting, batting .286 with a .729 OPS, but Oquendo said he has performed steadily in the field. He said Diaz shortened up his throwing motion to adjust to the speed of the game in the United States.

Contract issues could also enter the picture, as they often do. Diaz is on a guaranteed $4 million contract that expires after the 2017 season. The other young player bidding for the position, Greg Garcia, can be optioned to Triple-A.

If the Cardinals elect to go outside the organization, ESPN.com’s Adam Rubin reports that Ruben Tejada remains available despite a knee injury to New York’s starting shortstop, Asdrubal Cabrera.