MLB Pipeline ranks Jesús Luzardo and A.J. Puk as the A's top two prospects, as well as the No. 2 and No. 4 left-handed pitching prospects, respectively, in all of baseball.

Unfortunately for Oakland, both southpaws have dealt with arm injuries, delaying their major league debuts. Puk, 24, had Tommy John surgery last April, and Luzardo, 21, was shut down with a shoulder strain this March.

Now it appears there's finally reason for optimism. According to Athletics Farm, A's minor league pitching coordinator Gil Patterson expects the two lefties to begin pitching in games late next month.

A's minor league pitching coordinator Gil Patterson tells me Puk & Luzardo should both start pitching in real games in late June. Says Puk's been throwing in mid-90s & Kaprielian's been sitting around 91mph at Stockton. Said Gus Varland should be joining Stockton in couple weeks. — Athletics Farm (@AthleticsFarm) May 25, 2019

MLB.com's Martin Gallegos reported more good news on Luzardo, tweeting that he threw live batting practice Saturday and hit 96 mph on the radar gun.

Jesus Luzardo threw live BP in Arizona today and was hitting 96 mph. Good sign for A's. — Martín Gallegos (@MartinJGallegos) May 25, 2019

These obviously are welcome developments for the A's, who could use some depth in their rotation. If all goes well, both Luzardo and Puk might join Oakland later this season.

Right-hander Jharel Cotton also is on the mend from Tommy John surgery. The 27-year-old already has made two rehab starts at Single-A Stockton, allowing five earned runs on six hits in five innings, with five strikeouts.

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Of course, the A's biggest second-half addition likely would be Sean Manaea. The 27-year-old lefty had arthroscopic shoulder surgery last September and could return sometime after the All-Star break. Manaea has been throwing bullpen sessions this month, and has avoided any setbacks.

If the A's can stay in the playoff race for the next couple of months, it appears they could have some valuable reinforcements for the stretch run.