The positions in fantasy baseball differ in each league. Generally the offensive positions a fantasy owner will have to choose from include these: first baseman, second baseman, third baseman, shortstop, three outfielders, and a flex or utility (any offensive player). When it comes to pitchers, most leagues will allow the fantasy owner to select a set number of starting pitchers and relief pitchers, and then a set number of pitchers at either position, depending on the needs and preference of the owner. Other leagues offer the possibility of starting a designated hitter and a corner infielder (first or third baseman) and/or middle infielder (second baseman or shortstop).
Baseball has more potential statistical categories than any other sport. Most leagues use what is called a 5 x 5 statistical model: offensive players are credited for runs, batting average, home runs, runs batted in (RBI) and stolen bases; pitchers are credited for wins, saves, strikeouts, earned run average (ERA) and ratio (walks + hits divided by innings pitched, or WHIP). Other offensive categories include on base percentage (OBP), slugging percentage, on base plus slugging (OPS), hits, singles, doubles, triples, walks, and strikeouts. Other pitching categories include appearances, innings pitched, runs, earned runs, walks, losses, holds, strikeouts per nine innings (K/9) and strikeout to walk ratio (K/BB).
There are little things some custom leagues sneak in that you have to be aware of. Because custom leagues (as opposed to standard or default leagues) are allowed to use their own scoring systems and their own statistical categories, sometimes they sneak interesting things in. For example, some leagues will use caught stealing and strikeouts as offensive scoring categories. If you don’t pay attention to this before draft day, you may draft players who are good power hitters but prone to striking out, or players who steal a lot of bases but also get thrown out a lot. Watch for the different statistical categories these leagues throw in.