Any way you slice it, James Shields was the Tampa Bay Rays’ worst starting pitcher in 2010.

His 5.18 ERA was nearly a run higher than any of Tampa Bay’s other four regular starters, his 1.46 WHIP was also a rotation worst, and his staggeringly poor -1.3 WAR number was the worst of any Rays player – pitcher or otherwise.

League-wide, Shields allowed the most earned runs (117) and total bases (410) in the majors, tied for the most hits allowed (246), and allowed the second-most home runs (34).

If there was a weak link on a Tampa Bay staff that finished second in the American League with a 3.78 ERA en route to its second division title in three years, it was Shields.

This year, though, Shields has been the Rays’ Most Valuable Player.

As Tampa Bay fights to stay competitive with the New York Yankees and Boston Red Sox in its post-Carl Crawford era in the American League East, Shields has suddenly become one of baseball’s most dominant pitchers.

Entering Tuesday, Shields leads Rays starters in ERA (2.29), WHIP (0.96), strikeouts (117), strikeouts per nine innings (8.65) and innings pitched (121.2).

He is in the top five in the American League in each of those categories.

In four starts since June 6 — when the Rays went 14-6 over their last 20 games — Shields has gone 3-0 with a 1.06 ERA.

When he takes the mound Wednesday afternoon for a 12:10 p.m. start against Cincinnati, Shields will be riding a streak of three straight complete games, and will be going for his third shutout in his last four starts.

Besides Shields, only Roy Halladay, Cliff Lee and Justin Verlander have more than three complete games the entire season.

Since its initial postseason run in 2008, Tampa Bay’s success has been built on homegrown stars overachieving to counteract their big market division rivals’ high-powered free agents.

As the midway point of the season nears, Tampa Bay finds itself only 2.5 games behind New York and 2 games behind Boston entering Tuesday night’s action.

The Rays don’t have the spending power of those clubs, and they certainly can’t match either of those teams’ offensive firepower.

But if Shields can continue pitching like an ace, Tampa Bay will make a run at defending its division title.