This is a critical week in the market for shortstops, largely because of a player who is unknown to many U.S. fans.

The posting period of Japanese infielder Tsuyoshi Nishioka is set to expire on Tuesday. By 5 p.m. ET, clubs must submit a bid to Nishioka’s team, the Chiba Lotte Marines, in order to obtain exclusive negotiating rights.

Nishioka, a switch hitter with speed, is coming off a season in which he won the NPB Pacific League batting title. He has experience at shortstop and second base.

While it’s not clear which clubs are serious about bidding on Nishioka, a number of major league teams are looking to upgrade at his positions. If he agrees to come to the U.S., Nishioka could impact the trade market for shortstops – namely Tampa Bay’s Jason Bartlett.

Bartlett is drawing varied levels of interest from the Baltimore Orioles, St. Louis Cardinals, San Diego Padres and San Francisco Giants, according to major-league sources. The Rays could wait until after Tuesday’s announcement before aggressively pursuing a deal with one of the clubs that didn’t pair up with Nishioka.

It’s important to note that Nishioka won’t necessarily play next year in the U.S. The Oakland A’s submitted the winning bid for Japanese right-hander Hisashi Iwakuma, but contract talks between the A’s and Iwakuma’s agent have reached an impasse.

Bartlett, 31, is due to earn between $5 million and $5.5 million next year in salary arbitration. He is coming off a down offensive season, but batted .400 in the American League Division Series against Texas. He is scheduled to become a free agent after the 2011 season.

Bartlett is about as expensive as Boston shortstop Marco Scutaro, who also has been mentioned as a trade candidate. Scutaro has a guarantee of $6.5 million remaining on his contract, including the buyout of an option for 2012.

-Jon Paul Morosi