CLEARWATER, Fla.—Major league employment is often a zero-sum proposition.

Rodrigo Lopez being optioned to Triple-A, as he was on Monday before the big-league Phillies take on the New York Yankees at Bright House Field here, likely solidifies Aaron Cook’s spot.

Both were vying this spring to be sixth in the rotation, a deceptively important role.

Last year, eight pitchers started games for the Phillies. The National League average was 10.4. Only the Dodgers (7) and Reds (6) had fewer than seven starters.

Of Phillies 2012 starters, all but late-season Double-A callup Tyler Cloyd and relievers Raul Valdes and B.J. Rosenberg started 20 or more games.

Trades, injuries and ineffectiveness happen. Or, in the case of Roy Halladay, who was in uniform in the Phillies clubhouse for the first time since leaving the first inning of his start on Sunday against the Orioles, may have already started to.

If and when they do, Cook will now likely be the first guy the Phillies turn to.

Though it’s starting to look like management will need other options.

Lopez yesterday was shelled for seven earned runs on eight hits in two frames in a 17-10 loss to the Braves. He’d thrown seven scoreless innings over his three outings prior. He finished his Grapefruit League campaign with a 7.00 ERA in nine innings over four games.

Last year, Lopez threw in just four games with the Cubs last year. His ERA in three of the five years prior was over 5.00.

Cook was touched up yesterday, too, allowing three runs, two of them earned, in three innings. Three of his five outings thus far have been scoreless. In the other two, he’s had a 6.42 ERA.

In each of his last three big-league seasons, Cook has had an ERA over 5.00.

If it qualified, Cook’s 58.6 percent ground ball rate would’ve ranked second in baseball in 2012.

For Cook to be successful in his starts, if and when they come, the Phillies will have to take advantage of easy-out opportunities – something they’ve yet to do consistently this spring.