The Taiwanese lefty had never appeared in a Major League game, giving Yankees batters very little frame of reference regarding what pitches he would throw or how he would throw them.
But Chen hardly had the upper hand -- he remarked before the game that he knew only the most prominent Yankees by name, citing the global fame of stars Alex Rodriguez and Derek Jeter.
Chen allowed a home run to Jeter, the first batter he faced, but the lefty rebounded to give up only two earned runs in 5 2/3 innings.
Now, more than a month later, Chen has the experience that comes with six solid starts, but he still has a lot to learn.
"I still have a hard time to remember everybody's name from each team," Chen said through his interpreter. "But I've experienced a couple of outings right now, so I can remember their swing, their batting or how they stand."
Chen hasn't allowed more than three earned runs in any start this season and has been working on building up his stamina to pitch deeper into games.
On Thursday, Chen held the potent Rangers to two runs (one earned) in a season-high 7 2/3 innings, running his record to 3-0 and lowering his ERA to 2.43.
But while there was an element of surprise in Chen's six starts against unfamiliar foes, on Tuesday -- for the first time -- he will get a second look at an opponent.
"There's not many secrets in the game," O's manager Buck Showalter said. "They know his pitch sequence. They know what he features. There's a different look the first time they see him."
Chen said that being able to face the same lineup again hasn't changed his preparation.
His focus remains on going pitch by pitch, keeping the ball down and relying on his defense to make plays for him.
"I've still got my same routine," Chen said. "It doesn't matter if it's the Yankees or Boston or other teams; I still do my job."
Showalter said he's interested to see how Chen handles the adversity of a bad start, something he hasn't faced this season.
But until that happens, everything is positive for Chen. Not only is he pitching well, but he'll have his parents in attendance for Tuesday's game.
"That's pretty cool," Showalter said. "They're pretty excited. I tell you, they're all smiles, very happy with him."