PORT ST. LUCIE —- Frank Francisco’s first spring in a Mets uniform is going from bad to worse.

The team’s closer planed to have an MRI exam on his left knee Monday after encountering swelling in recent days. Francisco said the knee had been an issue earlier in spring training.

“Early in camp I felt a little sore in there and it went away,” Francisco said. “But the last three days I’ve felt soreness in there again, and that’s it.”

If Francisco needs a disabled-list stint, Jon Rauch would likely move into the closer’s role, although Bobby Parnell might warrant consideration based on a spring in which he has a zero ERA over 11 appearances.

Francisco had a rough outing against the Marlins on Saturday, when he surrendered two earned runs over two innings. The right-hander indicated the knee swelled up between innings, adding to his misery. He had the knee drained Sunday.

Francisco, who signed a two-year deal worth $12 million with the Mets over the winter, is 0-2 with a 5.54 ERA in 11 appearances this spring.

mpuma@nypost.com