SAN DIEGO (Interstat) — The St. Louis Cardinals and San Diego Padres, two of the National League’s top teams, meet Friday night at PETCO Park in a pivotal early-season series opener.

St. Louis (21-15) visits San Diego (22-14) after the clubs played to a scoreless draw Thursday. Right-hander Michael McGreevy (2-2) is the scheduled starter for the Cardinals. Right-hander Matt Waldron is expected to start for the Padres.

Waldron is a player to watch for San Diego. He tossed five innings of one-run ball Wednesday in a 5-1 win at San Francisco, allowing two hits and striking out seven. It was his second win in four starts, though he has been inconsistent, allowing six earned runs in consecutive outings April 23 and April 17.

For St. Louis, left-handed reliever Jared Shuster is a key arm out of the bullpen. He pitched two scoreless innings Wednesday in a 6-2 loss to Milwaukee, allowing one hit with a strikeout. He has not allowed an earned run in three of his last four appearances.

The Cardinals are coming off a 6-2 loss to the Brewers on Wednesday, their second defeat in three games. St. Louis took two of three from the Los Angeles Dodgers before that series.

The Padres won their series opener against the Giants 5-1 on Wednesday, snapping a two-game skid. San Diego has won five of its last seven.

The Interstat game simulator projects a 7-4 Cardinals victory. San Diego is a -1.5 run favorite, and the over/under is 7.5 runs.

The teams continue the series Saturday and Sunday before St. Louis travels to face the Athletics. San Diego heads to Milwaukee for a three-game set.