Shaun Marcum may soon have more clarity on the upper-back soreness that has been present during his last two starts.

A Mets spokesman last night said the veteran right-hander was headed to St. Louis for further medical evaluation today. Marcum underwent an MRI exam Tuesday on his upper back, but was cleared to pitch Saturday against the Brewers. Marcum allowed six runs, five of which were earned, on 11 hits over five innings.

Afterward, Marcum described his symptoms as including numbness, tingling and coldness in his hand.

Before the Mets beat the Brewers 2-1 yesterday, manager Terry Collins said he was toying with the idea of skipping Marcum’s next start, allowing the pitcher to have an extended rest through the All-Star break. Carlos Torres would be in position to join the rotation if Marcum needs a stint on the disabled list.

* Ruben Tejada, whose rehab assignment ended Saturday — he was optioned to Triple-A Las Vegas — will have to impress Mets brass in several areas before he’s considered for a return to the big leagues.

“I want to hear about quality at-bats,” Collins said. “I want to hear about the fact his first-step quickness is back. He’s not Jose Reyes, but he had great instincts to the ball and I want to make sure that I hear that is back.