Tatis landed on the shoulder after he made an unsuccessful attempt to catch a sinking line drive that became the pivotal play in the Mets' 1-0 loss to the Nationals. He was escorted off the field by trainer Ray Ramirez and was to travel by train to New York on Wednesday morning, so the full extent of the injury could be determined.
Nick Evans and later Endy Chavez replaced Tatis in left field. The two of them and Daniel Murphy now will share the position with the two rookies, Evans and Murphy, starting most of the games.
"It's very discouraging," manager Jerry Manuel said. "He's been a big and solid piece of what we are and what we've accomplished."
Soon after he join the Mets in mid-May, Tatis, 33, became an important contributor. A third baseman by trade, he moved to the outfield -- he had started 28 games in left and 35 in right -- and provided some of the right-handed run production the Mets had hoped to get from Alou. He finished his first big league season since 2006 with a .297 average, a .484 slugging percentage, 11 home runs and 47 RBIs in 92 games (273 at-bats).
Marty Noble is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.