DETROIT — Mike Napoli’s majestic homer began a rare early Boston breakthrough, Junichi Tazawa again bested Miguel Cabrera in a crucial spot and the Red Sox moved within one win of reaching the World Series by edging the Detroit Tigers 4-3 on Thursday night.Boston returns to Fenway Park with a 3-2 lead in the AL Championship Series. Game 6 is Saturday.Cabrera was thrown out at the plate in the first inning, halting an early Detroit rally, and he hit into a double play against Tazawa with runners at the corners in the seventh. The Tigers scored a run on the grounder, but it was a trade-off the Red Sox were willing to make.Napoli led off a three-run second with a drive off Anibal Sanchez into the ivy beyond the wall in center field.Detroit’s starters had allowed only three runs in 27 innings through the first four games of the series. After pitching six no-hit innings in Game 1, Sanchez allowed four — three earned — in six innings Thursday.Jon Lester allowed two runs and seven hits in 5 1/3 innings Thursday. He walked three and struck out three, and the Boston bullpen held on to finish off the fourth game of the series to be decided by one run.Down 4-2 in the seventh, the Tigers put runners on first and third with nobody out when Jose Iglesias and Torii Hunter singled. Cabrera, who struck out with runners at the corners against Tazawa in the eighth inning of a 1-0 loss in Game 3, hit a soft grounder to second for a double play this time.That was Detroit’s last stand in this one. Craig Breslow retired slumping Prince Fielder to end the seventh and got the first out of the eighth. Then Koji Uehara got five straight outs for the save.