Tyler Cravy (0-1) made an impressive major debut for Milwaukee, allowing a run on four hits in seven innings.
The Brewers won the series opener 1-0 and Milwaukee pitchers had thrown 19 consecutive scoreless innings before Reynolds’ RBI.
Lynn (4-4) struck out five and walked one in 7 2-3 innings.
Kevin Siegrist got the last out in the eighth and most of a sellout crowd of 42,835 stuck around to see Trevor Rosenthal earn his 16th save in 17 chances. The Cardinals are 6-2 with one game to go on the home stand.