Can James Shields Help the White Sox Make the Playoffs?

The MLB trading season has officially begun.

The Chicago White Sox -- sitting at 29-27, two games out in the American League Central heading into Sunday -- and San Diego Padres have agreed to a trade that would send James Shields to Chicago in exchange for two prospects, pitcher Erik Johnson and 17-year-old shortstop prospect Fernando Tatis Jr.

Shields may still be getting paid like an ace, but at this stage of his career, the 34-year-old is more like a No. 3 or No. 4 starter. In 11 starts this year (67 1/3 innings), he is 2-7 with a 4.28 ERA and a 4.42 FIP. He has struck out 7.62 batters per nine innings (not far off his career average of 7.84) and has walked 3.61.

Those numbers are skewed by his last outing, a disastrous performance against the Seattle Mariners in which he went 2 2/3 innings and gave up 10 runs on 8 hits and 4 walks with 1 strikeout and 2 home runs allowed. Heading into that game, Shields' ERA was 3.06 and opponents were hitting .256 off him. After that game, team executive Ron Fowler called the Padres' performance "embarrassing" and called out Shields specifically.

But up until that last disastrous start, Shields' 3.06 ERA ranked 22nd out of 51 qualified National League starting pitchers. And he has been very durable, making at least 31 starts in every season since 2007.

The deal has been rumored for about a week, with Chicago needing an upgrade in their rotation. While Shields is more of a mid-rotation guy than a top-end arm, he should be more productive that Mat Latos or Miguel Gonzalez. Latos is 6-1 in 10 starts, but he has a 4.02 ERA and has seen that ERA climb steadily over his last six starts. Latos has not pitched more than 6 1/3 innings in any start this year. Gonzalez has a 4.09 ERA in six starts with Chicago, with a FIP of 4.55.

Still, the White Sox rotation has held its own this season, and adding Shields won't hurt. They come into Sunday tied with Toronto for the best fWAR among starters at 5.7, with a 3.64 ERA that ranks third in the American League and a FIP of 4.05 that checks in fourth.

Like most pitchers who enter their mid-30s, Shields has seen his fastball velocity fall, averaging just 90.1 miles per hour this season, down from 91.0 last year and down from the low 92's he was typically at throughout his career. The good news is that as Shields leaves pitcher-friendly Petco Park in favor of the homer haven known as U.S. Cellular Field, he's a pitcher who generally keeps his fly balls allowed to a minimum. Just 31.1% of all batted balls allowed are fly balls, which puts him in the bottom half of National League pitchers.

He is, however, prone to giving up a lot of home runs, too. Last year he allowed a National League-high 33 home runs, and Shields has twice led the league in home runs allowed.

On the other end of it, the deal confirms that the signing of Shields by San Diego before last season was pretty much a disaster. He is in the second year of a four-year, $75 million deal, one that pays him $21 million per season in each of the next three years (he has a player opt-out clause after this season but he, unlike most players who put those in their contract, is unlikely to exercise it this offseason). San Diego will pick up more than half of Shields' salary moving forward as the team begins a full-on rebuild.

As for what Chicago gave up to get him, it wasn't much. Johnson is expected to take Shields' place in the San Diego rotation. In 18 career MLB starts, Johnson has an ERA of 4.50 and a FIP of 5.68, striking out 7.07 batters per nine innings with a high walk rate of 4.50 per nine innings. Tatis Jr. is just 17 years old and was not ranked as one of Chicago's top-30 prospects before the start of the season.