The Cardinals, whose starting pitching has been very solid all season, nevertheless are attempting to strengthen it even more before Tuesday's trade deadline in an effort to chase down the Reds and Pirates in the NL Central.

The Redbirds have been engaged in discussions with the Rays for starting pitcher James Shields and with the Twins for left-hander Francisco Liriano, according to CBSSports.com sources. They also tried to sign veteran Ben Sheets before the right-hander eventually signed with the Braves.

The Cards rotation ranks fourth in the NL with a 3.55 ERA and, until Lance Lynn lasted just five innings Friday in Chicago, compiled a streak of 21 consecutive games in which the starting pitcher worked at least six innings.

However, now that they know ace Chris Carpenter will not return in 2012, they apparently have decided that the best way to catch the first-place Reds and second-place Pirates is to strengthen their rotation. The Cardinals trailed Cincinnati by 5 1/2 games entering play Saturday.

A Liriano trade is "likely to happen", according to one person familiar with the Twins' trade discussions. The Orioles, Cardinals and Angels are among several clubs that have been discussing Liriano with Minnesota, although the Angels effectively removed themselves from those talks when they acquired Zack Greinke from the Brewers on Friday.

The veteran Twins' lefty is 3-10 with a 5.31 ERA in 22 games, 17 starts. He next is due to pitch Sunday against the Indians.

Several clubs are engaged in discussions with Shields, as colleague Jon Heyman writes here, including the Rangers, Dodgers, Braves, Indians and Cardinals.

Shields said in Anaheim on Friday night that he's hoping that a trade does not materialize and he is able to stay with Tampa Bay.