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Did Steve Young play any notable games while as a backup?
In their 1987 divisional playoff game against the Minnesota Vikings, he replaced Montana in the second half after the team fell behind 27–10.
Did Steve Young win the 1987 divisional playoff game against the Minnesota Vikings?
The 49ers still lost the game, but Young had a good performance, completing 12 of 17 pass attempts for 158 yards and a touchdown.
Did Steve Young play any other notable games as a backup besides the 1987 divisonal playoff game against the Minnesota Vikings?
On October 30, 1988, Young ran for a 49-yard, game-winning touchdown against the Minnesota Vikings.
Did Steve Young play any other notable games as a backup?
The Minnesota Vikings.
When were the 49ers vs the Minnesota Vikings being played?
On October 30, 1988
Was 49ers vs. Minnesota Vikings played at the 49ers stadium or the Vikings stadium?
The Vikings' playoff win the previous season hung over San Francisco Candlestick Park as Coach Walsh started Steve Young in Joe Montana's stead.

Question: Did the 49ers play well during the 1987 to 1990 period?
Self-contained rewrite: Did the 49ers play well during the 1987 to 1990 period?