Is it bad to enter the NCAA tournament on a long winning streak? Yes.

(updated through 2016 tournament)

In the 32 NCAA tournaments of the six-round era, which began in 1985:

- 16 champions (50%) lost their final pre-tournament game, including the last 3 in a row

- 26 champions (81%) entered with a winning streak of five or fewer games

The only exceptions:

1986 Louisville - won 11 entering tournament, 17 in a row overall

1992 Duke - won 7 entering tournament, 13 overall

1995 UCLA - won 20 entering tournament, 26 overall

1998 Kentucky - won 7 entering tournament, 13 overall

2008 Kansas - won 7 entering tournament, 13 overall

2013 Louisville - won 10 entering tournament, 16 overall

The longest single-season winning streak to fall during a tournament?

2015 Kentucky - 38 in a row

In the earlier years of the NCAA tournament (pre-1985), an era of significantly less parity, long winning streaks were much more common among champions:

1941 Wisconsin - won 14 in a row to end the season

1943 Wyoming - won 29 in a row to end the season

1948 Kentucky - won 16 in a row to end the season

1955 San Francisco - won 25 in a row to end the season

1956 San Francisco - went undefeated, 29-0 (so this was a 54-game streak overall)

1957 UNC - went undefeated, 32-0

1961 Cincinnati - won 22 in a row to end the season

1962 Cincinnati - won 18 in a row to end the season

1964 UCLA - went undefeated, 30-0

1965 UCLA - won 15 in a row to end the season

1967 UCLA - went undefeated, 30-0 (so this was a 45-game streak overall)

1968 UCLA - won 16 in a row to end the season

1971 UCLA - won 15 in a row to end the season

1972 UCLA - went undefeated, 30-0 (so this was a 45-game streak overall)

1973 UCLA  - went undefeated, 30-0 (so this was a 75-game streak overall)

1974 NC State - won 28 in a row to end the season

1976 IU - went undefeated, 32-0

1978 UK - won 13 in a row to end the season

1982 UNC - won 16 in a row to end the season

1984 Georgetown - won 12 in a row to end the season


So the answer to the question posed in the post title would, statistically, be yes.  It's been rare for teams to keep momentum all the way through March and April, especially since the tournament expanded to six rounds.