Joe DiMaggio sucked in the World Series.

In the regular season Joe DiMaggio struck out every 18.59 At Bats (AB).  In the World Series (WS): every 9 at home, every 8.38 on the road.

In 90 AB at home Joe DiMaggio had only four RBI.  FOUR.  That's one fewer than the number on his back.

All eight of Joe DiMaggio's (WS) Home Runs (HR) were hit on the road.  Here are the home/road splits for the three other Yankee greats:

Mantle 5/13
Ruth 4/11 Including one in the Polo Grounds in 1921 WS.
Gehrig 4/6.

So none of the big four hit more HR in their home parks.  Babe Ruth hit all of his WS HR for the Yankees, none for the Red Sox.

Eight of top ten in WS At Bats (AB) are Yankees (with Plate Appearances (PA)):
1. Yogi Berra 259 295
2. Mickey Mantle 230 273
3. Joe DiMaggio 199 220
4. Frankie Frisch 197 216
5. Gil McDougald 190 215
6. Hank Bauer 188 199
7. Phil Rizzuto 183 219
8. Elston Howard 171 189 Some with Boston.
9. Pee Wee Reese 169 191
10. Derek Jeter 156 173

DiMaggio is number three with 199 AB.

Top ten in WS HR with PA:
1. Mickey Mantle 18 273
2. Babe Ruth 15 167
3. Yogi Berra 12 295
4. Duke Snider 11 149
5. Lou Gehrig 10 150
  Reggie Jackson 10 116
7. Joe DiMaggio 8 220
  Bill Skowron 8 141
  Frank Robinson 8 106
10. Gil McDougald 7 215
  Hank Bauer 7 199
  Goose Goslin 7 143
  Chase Utley 7 49

Let's put some of this together.

Top Yankees WS HR, AB (click link to see detailed data):
Mickey Mantle 18 230
Babe Ruth 15 118 Excludes 11 WS AB with Boston.
Yogi Berra 12 259 Includes regular season data with Mets.
Lou Gehrig 10 119
Joe DiMaggio 8 199
Bill Skowron 8 133 Includes 1963 WS as Dodger against Yankees (HR in Yankee Stadium).
Gil McDougald 7 190
Hank Bauer 7 188 Includes regular season data with KC.

Only DiMaggio and Berra had a better HR rate (AB/HR) in the regular season than in WS and Yogi's was almost even, about 21.5 to 21.  DiMaggio was 25 to 19, a significant difference.

Click this link.  There are several tabs with data comparing a player's On Base Plus Slugging (OPS): regular season v. WS with the percentage difference.  Here are those WS percentages for Joe DiMaggio:

1936 -9.61%
1937 -40.29%
1938 -18.82%
1939 -26.59%
1941 -48.64%
1942 -20.82% Yankees lost.
1947 -7.69%
1949 -53.87%
1950 10.68%
1951 1.14%

We don't hear much about this because the Yankees won nine of those ten WS.  Yogi Berra is considered a clutch player because of his batting in his later WS but Yogi sucked in his first five.  Yankee outfielder Hank Bauer, who holds the WS hitting streak record at 17, had a WS career similar to Berra's.  Jackie Robinson lost all but one WS and his numbers sucked:

1947 -16.7%
1949 -36%
1952 -23%
1953 -18%
1955 -17.5% Dodgers won.
1956 .09%

The only thing more shocking than DiMaggio's poor WS performance is that hardly anyone knows just how bad he was.