Playing their third game in a span of three and a half days caught up with the Blues in the third period of Sunday’s game against the Pittsburgh Penguins at Scottrade Center.

A pair of defensive mistakes, one by rookie Vince Dunn and one by team captain Alex Pietrangelo, led to goals that carried the Penguins to a 4-1 victory.

The Blues were coming off perhaps two of their best games of the season, a win at home over Colorado on Thursday night and at Winnipeg on Friday night, and were tied 1-1 against the defending Stanley Cup champions headed into the third period.

Just seconds into the period, the Blues thought they had grabbed the lead on a goal by Paul Stastny, deflecting a shot by Pietrangelo. A video review determined Stastny’s shot came off a high stick, however, and the call on the ice was overturned.

Just seconds later, a pass from Dunn was intercepted by Bryan Rust and he skated in alone and beat Jake Allen to give the Penguins the lead.

Midway through the period, Pietrangelo was too casual playing a puck behind his own net and gave it up to Dominik Simon, leading to a goal by Riley Sheahan that increased the lead to 3-1.

The Blues pulled Allen with just under three minutes to play during a faceoff in front of the Pittsburgh net, but Sidney Crosby won the draw against Stastny and later in the shift scored an empty net goal to cap the Penguins’ win.

The goal was the second of the game for Crosby, whose goal in the second period – the 400th of his career – tied the game just 21 seconds after the Blues had taken the lead on a goal by Kyle Brodziak.

Matt Murray stopped 33 of 34 shots by the Blues while Allen had 19 saves on 22 shots by the Penguins.

Worth noting:
The Penguins have the top-ranked power play in the NHL but were 0-for-2 on Sunday … The loss dropped the Blues record at home to 19-12 … Allen’s last win at home came on Dec. 10 … Crosby did not have a goal against the Blues in his first 10 career games against St. Louis but has now scored seven goals in his last six games, including five in his last three games dating back to the end of last season.

Looking ahead:
The Blues will go on the road for two division games this week, playing Tuesday night in Nashville and Friday night in Dallas.