PITTSBURGH -- Josh Harrison led off the bottom of the first inning with the first of three home runs by the Pirates, Gerrit Cole pitched six innings of one-run ball and Pittsburgh held on for a 5-4 victory on Monday in its home opener.

The Tigers (6-1) scored three runs in the ninth inning but wound up losing for the first time this season; they had outscored opponents 47-16 in their first six games.

The Kansas City Royals (6-0) are now the lone unbeaten team in the major leagues.

The Pirates (3-4) won their third game in a row as first baseman Pedro Alvarez and pinch hitter Corey Hart added home runs during a three-run seventh inning off Anibal Sanchez (1-1) that extended Pittsburgh's lead to 5-1. Hart's homer was his 1,000th career hit.

Pirates closer Mark Melancon barely held the four-run lead in a non-save situation as he gave up an RBI double to first baseman Miguel Cabrera and a two-run home run to right fielder J.D. Martinez before inducing third baseman Pedro Castellanos to hit into a double play and striking out pinch hitter Victor Martinez.

Cole (1-0) allowed three hits in six-plus innings, with eight strikeouts and two walks. The 6-foot-4 right-hander was pulled after the Tigers, trailing 2-0, loaded the bases with none out in the seventh.

Hughes escaped the jam by allowing only one run, which scored on Castellanos' double-play grounder.

Sanchez (1-1) lost his fourth straight start against the Pirates. The right-hander had nine strikeouts in 6 1/3 innings but also gave up five runs and eight hits.

Harrison, the third baseman, had two hits for the Pirates. Cabrera and left fielder Yoenis Cespedes also had two hits each for the Tigers. Cabrera is 13-for-18 with seven RBIs in his last four games.

The Pirates carried over their strong play at PNC Park from recent seasons. They are 102-61 at home since the start of the 2013 season and have won five straight games over the Tigers at PNC Park, along with 11 of the last 14.

Harrison hit a drive to the right-center field stands on Sanchez's first pitch of the game, sending the crowd of 39,333 --- a regular-season record at PNC Park --- into a frenzy.

Center fielder Andrew McCutchen's sacrifice fly in the third inning increased the Pirates' lead to 2-0.

After the Tigers drew within a run in the top half of the seventh, the Pirates made it 5-1 on a leadoff homer by Alvarez and a two-run shot by Hart.

NOTES: The Pirates activated LHP Francisco Liriano from the paternity list and optioned RHP Casey Sadler to Triple-A Indianapolis. Liriano missed his scheduled start Sunday at Milwaukee after his wife gave birth to a daughter, the couple's fourth child. He is scheduled to pitch Wednesday against the Tigers. Sadler notched his first major league win Sunday as he held the Brewers to two runs and four hits in five innings. ... Pirates CF Andrew McCutchen was in the lineup for a second consecutive day after sitting out Saturday night at Milwaukee because of left knee soreness. McCutchen said he plans to keep playing through the soreness. ... Tigers DH Victor Martinez did not start Monday and will not start any of the three games in the series as the designated hitter is not in effect during interleague series in National League parks. Martinez can play catcher and first base, but the Tigers do not want him playing in the field after he underwent arthroscopic surgery on his left knee Feb. 10. ... The series continues Tuesday night with Tigers RHP Shane Greene (1-0, 0.00) facing Pirates RHP A.J. Burnett (0-0, 3.38).